Purple stained fingers, purple stained tongue, purple antioxidants for your digestion, and incomparable purple sweetness, all before school lets out at the end of May. But they aren’t all purple, and they don’t all stain.
For many gardeners the early sweetness of mulberries is the essential fruit to break the long berry-less winter. But for mulberry lovers, a strategic planting of several varieties can result in delicious mulberries all summer long. The fresh sweet taste, coupled with the burst of healthy energy and the easiness of growth, make mulberry trees one of the best for any garden. There are a handful of mulberry varieties to choose from, but first let’s dive into some history.
Geographical Range
It may seem like mulberries have been around for ages and come from all over the map. Well, they kinda do. They have been around since the fossil record and consumed by animals of every size and shape.
The White Mulberry (Morus alba) has its origins in Eastern China, as do many others, including Morus notabilis, the mulberry species believed to be the genetic base for all other mulberry species. The White mulberry was brought to Europe by the Romans and grown there for their medicinal qualities.
The Red, or American mulberry (Morus rubra) is native to, and common in the Eastern United States. Until the white mulberry was introduced to the United States (for silk production during colonial times,) it managed to survive genetic isolation. Now most Red Mulberries carry some White Mulberry genes. Nothing wrong with that, the fruit quality of these hybrids are often superior.
The Himalayan Mulberry/ Shahtoot (Morus macroura) is native from the Himalayas to Southern Asia.
Black Mulberries are thought to have originated in Southwest Asia, but have been grown in Europe for centuries. 10,000 trees were purchased by King James I around 1607 and planted in a large garden near Buckingham Palace in an effort to establish silk manufacturing to compete with France. Unfortunately, it is white mulberries that silkworms favor, and the investment failed, but some of the trees remain to this day.
More about Species
Differentiating mulberry species and varieties can be challenging. Mulberry varieties easily hybridize making it very difficult to know exactly what species you have. Plants that are easy to propagate such as figs, guavas, dragonfruit, and mulberries also lose distinct identification as cuttings are passed around; I can’t tell you how often I hear “I forget which one this was!” Understanding why this is important will become clearer as we get into specifics.
To briefly get into the weeds- or the trees for that matter, the genus classification is quite complicated due to various geographically isolated and genetically distinct strains, and an extreme propensity for hybridization among most varieties. Some taxonomists include as many as 200 distinct species, but only about 10-17 are officially recognized, and even those do not necessarily have clear genetic origins. The following are the most widely known and cultivated species, followed by a short list of others recognized:
MOST WIDELY CULTIVATED SPECIES:
White Mulberry (Morus alba) Eastern China
Australian Mulberry/ Chinese Mulberry/ Korean Mulberry (Morus australis) Southeast Asia
Himalayan Mulberry/ Shahtoot (Morus macroura, syns. M. laevigata, M. alba var. laevigata)
Himalayan Mulberry/ Shahtoot (Morus serrata, syn. M. alba var. serrata)
Black Mulberry (Morus nigra) Southwest Asia
Red Mulberry/ American Mulberry (Morus rubra) Eastern North America
Mongolian Mulberry (Morus mongolica, syns. M. alba var. mongolica, M. mesozygia) Central and South Africa
OTHERS RECOGNIZED INCLUDE:
Hua Sang (Morus cathayana) Eastern Asia
Texas Mulberry (Morus celtidifolia, syn. M. microphylla) Native from Arizona and Oklahoma south to Argentina
Silkworm Mulberry (Morus indica, syn. M.alba var. indica) Sub-tropical Himalayas
Evergreen Mulberry (Morus insignis) Central and South America
Japanese Mulberry (Morus japonica)
S.S. Chang (Morus liboensis) Guizhou, China
The Mulberry Tree (Morus notabilis) Yunnan and Sichuan provinces of China (2n=14 chromosomes suggest this is the basal species for all others)
Three Lobed Mulberry (Morus trilobata, syn. M. australis var. trilobata)
(Morus wittiforum)
Since the vast majority of popular mulberry cultivars on the market belong to only four species classifications and their hybrids, the rest of the post will specifically refer to those. They are Morus alba (White Mulberry), Morus rubra (Red Mulberry), Morus nigra (Black Mulberry), and Morus macroura (Himalayan Mulberry). In order to fully understand distinctions between cultivars we will provide general information first, then a sampling of varieties near the end of the post.
Description
Lifespan
Morus rubra (Red Mulberry) is generally one of the shortest lived species reaching a maximum lifespan of about 75 years.
Morus macroura (Himalayan Mulberry) and Morus alba (White Mulberry) may live for as much as 100-250 years in ideal conditions, depending upon the cultivar.
Morus nigra (Black Mulberry) has a fruitful lifespan of between 500 to 1000 years. Many of those planted in the early 1600s in Great Britain by King James I are still alive and well.
Rate, Habit and Height
Mulberry trees vary greatly in size by variety and growing conditions, from cultivars Morus nigra ranging from about head high to 30 feet, to some Morus alba trees reaching as much as 80 ft. In rich soils of the warmer parts of the southern United States Morus rubra can grow as tall as 70 feet.
Roots can be thirsty and somewhat aggressive, finding their way into irrigation pipes, septic or sewer systems, or lifting and staining concrete that is in close proximity. To prevent potential damage to concrete and irrigation infrastructure many varieties may be kept as dwarfs or kept smaller when contained in tubs and pots. Most varieties will perform well in pot culture. Ultimate size, though somewhat affected by environmental conditions, is primarily determined by cultivar.
Most mulberry trees grow fast, but are dependent upon warm temperatures to do so. Morus nigra grows more slowly.
While most mulberries manifest rounded or spreading canopies, Morus alba and its hybrids have the greatest variability in form, including weeping, tiered and conical shapes. Morus nigra generally manifests a shrub form unless trained.
Foliage
All mulberry species grown in the continental United States are deciduous. One species, morus insignis, which is native to Central and South America, is evergreen. Mulberries break dormancy in spring based on temperature, not day length. Variability in the number of warm days required for bud break is dependent upon cultivar, with Morus nigra generally leafing out later than other species.
Leaves are serrated, variable in shape from spade to lobed, and often are variously lobed on the same plant, even unsymmetrical. Morus rubra has more consistent and prominent lobes than Morus alba. Mulberry leaves are green in spring and summer turning shades of yellow in fall. The leaves of Morus alba possess a shiny appearance on the upper side while those of Morus nigra appear dull and fuzzy. The milky sap from all species of Morus may cause skin irritations, but none have thorns.
Roots
The roots of mulberries are aggressive and usually fairly shallow- no more than 2 feet deep, extending laterally beyond the tree’s drip line as much as 1 ½ times as far from the trunk as the tree is tall. Having excavated some trees myself, I can attest that the lateral roots also have vertical sinker roots that are smaller in diameter. As may be mentioned several times, it is recommended to plant these trees far enough away from structures and plumbing infrastructure to avoid potential problems.
Flowers
Mulberry trees are either dioecious (male and female flowers on separate plants) or monoecious (male and female flowers on the same plant), and sometimes mulberry trees will change from one sex to another (sequential hermaphroditism or dichogamy).
Male trees produce excessive amounts of allergy-causing pollen and therefore have won a place on the list of nuisance trees in many municipalities. Parthenocarpic cultivars are female trees that produce fruit without pollination or male trees.
Flowering occurs in spring, spring and fall, or sporadically throughout the warm season, depending on the specific cultivar.
The flowers often appear in multiples in the axils of this season’s new growth and spurs on older branches. The flowers are pendulous green catkins. They are wind pollinated and many cultivars do not produce pollen and will set fruit without any pollination. Cross-pollination between genetically distinct individuals is not necessary for mulberries to set fruit. Most cultivars sold at nurseries are parthenocarpic and set seedless fruit without pollination, but a few cultivars require a second tree as a pollenizer. Those only produce fruit if pollinated, and produce seedy fruit once pollinated. These are generally not recommended.
Fruit
Botanically a mulberry is not a “berry” but a syncarp, a collective aggregate of individual fruits. The flowers form on catkins. Once pollinated they swell to form a collective fruit cluster that resembles a blackberry.
As we often find fruit of varying degrees of white to pink to red to purple-black, it is often thought that the fruit color is the meaning of the common appellations of “White” or “Red” or “Black”, but that is a mistake. Morus alba, which means “white” may appear in any of those colors. The differentiation of mulberry varieties by the common name “Red,” “White,” or “Black,” does not actually refer to the color of the fruit, but rather to the color of the leaf buds on the dormant twigs.
Many growers prefer cultivars of Morus alba over Morus rubra types because cultivars of Morus alba and their hybrids tend to be non-staining. That’s right, no matter the color of the fruit, not all of these delicious berries stain fingers, clothes, driveway, and tongue. ‘Pakistan’ and several other cultivars provide the sweetness without the stain, though the juice may be red or transparent white. So sweet are some berries that In the Middle East these are often dried and used as a substitute for table sugar, though because of the flavor tones that pigmentations give to the fruit during dehydration, white colored fruit often provide the closest to a raw sweet.
Taste
While the flavors are often distinctively different from one species to another, it is a general finding that white mulberries (Morus alba) are considered the sweetest of the various species, having a higher Brix (sugar content), yet lack the needed tartness to provide a complexity of flavor that the others contain.
Red mulberry (Morus rubra) fruits are usually nearly black in color. The best red mulberries may be comparable in flavor to the black mulberries (Morus nigra), though the black mulberries generally are considered the most desirable combination of sweet and tart.
That said, taste tests have been done to determine which mulberry varieties are generally favored and the results are across the board. Individual taste preferences vary, some people preferring the sugar sweet, others preferring the complex flavor. A berry’s flavor will always depend on its ripeness, freshness, cultivar, soil moisture, terroir (soil characteristics that lend to flavor), and sunlight.
Cultivation
Temperatures
White mulberries (Morus alba) species enjoy the widest range in cold tolerance- experiencing damage anywhere from 25° F to well below -25° F, depending upon the cultivar and the characteristics of the individual clone and its environment. Red mulberries (Morus rubra) are hardy to somewhere below 0° F. Black mulberries (Morus nigra) are generally limited to 0° to 10° F average minimum temperature or warmer, but again, it still manifests quite a range in tolerance. These have not been planted extensively in the United States, and so we do not have the extent of data for black mulberries as we do for other varieties. The majority of Black mulberry specimens have been planted on the Pacific Coast.
While mulberries are tolerant of heat, fruit production is highest from 75-85°F and then drops significantly. At 90°F fruit production stops.
Chill hour requirements for mulberries, or the accumulated hours between 32-45°F, are listed as under 200, but possibly do not need any. Mulberries are listed as hardy in USDA hardiness zones 5-11, depending upon the cultivar.
Location/ Planting
While mulberries may be able to grow in filtered light they need full sun and well-draining soil to be able to thrive and produce.They also need adequate space. Because the trees are flexible and wind resistant smaller cultivars may be planted 10’ apart for espaliers, hedgerows, and windbreaks. Plant at least 15 ft apart for larger cultivars, away from sidewalks, patios, and 20’ away from foundations to avoid potential damage by roots. Fruit from many varieties will stain concrete and the sticky residue may be tracked indoors causing purple stains on carpet and linoleum, and endless regret. Plant 50′ away from water pipes that are not specifically serving the tree, sewer lines, and septic systems, as the roots can quickly cause damage to water infrastructure. Various dwarf cultivars may also be grown in containers.
When transplanting a mulberry tree, dig a hole as deep as the root ball and about 2-3 times as wide. If the native soil is very compact consider doing a drainage test. Dig the hole partially or completely, then fill with water. If it takes 24 hours to completely drain then your soil is too compact and you can expect root rot later on. It will be necessary to widen the hole and dig vertical drainage channels down below the hardpan that is preventing the drainage.
Once the hole is dug carefully remove the tree from its container and inspect the root ball. Large, circling roots may eventually cause girdling, slowing the tree’s growth and potentially killing it. If planting during the dormant season it is recommended to carefully wash soil off the roots, untangle them, remove damaged and problematic roots, and spread the roots out in the hole as a bare-root tree.
The tree trunk should be planted at the same depth that it was in the pot or slightly shallower. Showing the initial root flare should be ok. You may use the soil that was in the container to mix with native soil, or plant the tree directly in native soil leaving the potting mix and compost as a topdressing of several inches. This ensures that the roots are able to naturalize in the native soil environment, but still receive the benefit from whatever soil organisms and nutrients were in the soil that was in the pot to begin with.
Soil
Mulberries are tolerant of many soil types as long as they are well-draining, but thrive in a warm, deep loam. Shallow alkaline soils such as those frequently found on chalk or gravel are not recommended and may result in substantially slower growth and signs of iron chlorosis. Mulberries have shown a moderate tolerance to salt.
Water
Although drought tolerant for short periods once established, mulberries really need to be watered during dry spells. If the roots become too dry, the fruit is likely to drop before it has fully ripened.
Water deeply using flood or basin irrigation regularly the first two years to ensure a healthy root system. Ensure irrigation monthly during dry seasons, and weekly during fruit set and ripening. By limiting water supply in the fall you can encourage the tree to enter dormancy. Using a coarse wood chip mulch at the base of trees, kept a foot away from the trunk or so, will help to reduce evaporation and excess heat.
Fertilization
If planted in decent soil, your mulberry tree shouldn’t need much in the way of supplemental nutrients. If desired, an organic fertilizer may be applied after several months of active growth. If you are used to using chemical fertilizer, using a balanced one such as 10-10-10 should work but wait until the tree has been in the ground for a year or longer. Never fertilize during bloom season or fruit set, or the tree will drop its bounty prematurely.
In the desert Southwestern United States, as long as the tree is planted in a good sandy loam with plenty of moisture a slow release nitrogen fertilizer application around Valentine’s day is usually sufficient. Dwarf trees may appreciate an extra dose of organic nutrients in late spring and late summer. Too much nitrogen will result in fast growing, long, weak shoots that are prone to wind breakage. In areas where your particular tree may be borderline frost sensitive too much nitrogen may also cause the tree to be susceptible to freeze damage.
Pruning
Pruning is not recommended on mulberries during the first year in the ground. The root system should be allowed to attain sufficient development the first year for successive healthy growth. Depending upon the desired shape pruning may not be necessary at all except to remove crossovers in the center of the canopy. This is more often needed in Morus alba and Morus macroura.
Very little pruning should be needed once the branches are trained into the desired framework, other than for removal of dead or overcrowding branches in the crown. Fruiting spurs can be encouraged from the 6 lowest buds on each branch through strategic peak summer pruning. By tip pruning branches from the tree during this time you can limit growth, but allow the maximum fruiting buds for next year. However, it is critical that pruning during the active growth season is minimal to prevent excessive bleeding.
Mulberry trees bleed heavily, but are also susceptible to some diseases in cool weather, so the vast majority of pruning should be done near the end of the dormant period. Careful dormant pruning in late winter, early spring, about two weeks before bud-break will ensure quick healing and encourage strong spring growth. For us in Maricopa County, Arizona that’s when daily lows are about 50° F, or the beginning to mid-February, or just before Valentines Day.
Anything pruned over 2” in diameter at any time of year may not ever entirely heal. Large open wounds will continue to dehydrate throughout summer. Avoid pruning more than 25% of the tree annually to prevent sending the tree into shock. Shock can begin the tree on a decline of disease susceptibility that is very difficult to recover from.
ESPALIERING
Mulberries, particularly dwarf types and Morus nigra, respond quite well to espaliering. By training branches horizontally the fruiting buds and spurs will form closer together and will often fruit heavier for a given space. Train as you would grape cordons.
ROTATIONAL COPPICING
Another technique commonly used in colder climates to ensure that the tree stays within a manageable size for frost protection and harvest, or warmer climates simply to control size, is to coppice branches rotationally. This is done by cutting the central trunk low, beginning when still young. Many new leaders will grow from the base. Select one leader per year to keep for three years and trim off everything else during dormancy that is 3 or 4 years old. This ensures that each year the tree will have strong new growth that never achieves more than a three year height. This technique somewhat resembles cane pruning for grapes. As most of the crop is formed on new wood, only long-term fruiting spurs are sacrificed.
POLLARDING
Lastly, a note about pollarding. Pollarding is a technique of pruning mulberries, particularly fruitless mulberries for coppice wood, that achieved some level of popularity in the United States in recent decades. It was originally practiced to prevent grazing and browsing animals from reaching the branches. This pruning system encourages all new, uniform growth each year, similar to coppicing, but from a main set of head-high scaffold branches.
Pollarding training begins when the tree is still young; an initial scaffolding is selected and headed back to a chosen height. Each year the new growth is headed back to the same area of scaffolding, never cutting past the original scaffold, or last year’s cuts. Over time large knots, or knuckles form where branches have been successively pruned off.
While this technique provides a very uniform globose canopy, the branches are long and wispy, and in some climates, such as the desert southwest, the tree may not be as healthy, and much fruit will be sacrificed for new growth and appearance, as the majority of fruit forms on last seasons new growth.
Propagation
Most varieties of mulberries are especially easy to propagate by grafting, layering, or rooting, with or without rooting hormone. It is not uncommon for individuals making a wattle fence out of mulberry branches trimmed off in late-winter, to find them rooted out and grown in place, ultimately creating an unintentional living barrier.
PROPAGATE BY SEED
You would think that if you had mulberry trees popping up in your yard or neighborhood that the germination rate of mulberry seed would be high, but actually it’s pretty low. Mulberry’s propagation success can primarily be attributed to strength in numbers. Seeds used must be freshly extracted from the fruit and not allowed to fully dry out.
Starting Morus alba, Morus macroura, and Morus rubra mulberries from seed requires cold stratification for as much as 4 to 16 weeks in order to maximize germination and prepare the seed to sprout. After cold stratification seeds have a better success rate if sown shallowly in a well draining starting mix and kept moist. Once germination occurs they will need 12-16 hours of bright, indirect light, or filtered light through a sunny window. Harden off seedlings outdoors under filtered light for a couple of months.
Young trees under 2 years old should be taken indoors during freezing temperatures, or under shade during excessively hot temperatures. This is because the temperature hardiness of your young tree seedlings will not yet be known.
While mulberries may be grown from seed, it is generally not recommended. Trees can take 10 or more years to bear fruit, and until then it will be unknown whether they will be male, female, or parthenocarpic. Males will be mostly useless in a food production system and females that require pollination will result in seedy, crunchy fruit, assuming they have a male to pollinate them, otherwise there will be no fruit at all. Black mulberries (Morus nigra) will often take up to 15 years before full production.
PROPAGATE BY GRAFTING
Understanding the ultimate size of the variety you want to grow and the virtues of any rootstocks available may provide you with an advantage in selection. Some larger desirable cultivars such as “Pakistan” may be “dwarfed” by grafting using the rooted cuttings of cultivars such as “dwarf everbearing” as rootstock, effectively reducing the ultimate size of the tree to just larger than the rootstock itself would grow- maybe 12-15 feet tall instead of 30-80 feet.
Mulberries are most often grafted via shoot budding, veneer grafting, or cleft grafting. Shoot budding is begun by making a T-cut in the rootstock to be used. Then, a gradually sloping, smooth diagonal slice is made on the lower portion of the scion to be used. The scion is trimmed to 1-2 buds, inserted into the T cut, then wrapped and sealed with parafilm or grafting paste.
In dry climates, such as where we live, here in Arizona, a higher success rate on most grafts is achieved when the vertical tip of the scion is also sealed to minimize drying out. Other types of grafts such as veneer grafts and cleft grafts also bear satisfactory results.
Grafting mulberries are most often successful if done before the sap is really flowing, but after the bark slips, 2 weeks prior to bud-break. If sap is flowing it may interfere with the proper fusing of the graft. To address this I have recently heard about a method for dealing with problematic bleeding during grafting.
Before making the grafting cut, first make a small perpendicular cut about an inch below the area to be grafted to bleed off extra sap before it gets to the grafting area. Then prepare your scion wedge with one or two buds and carefully wash it in clean water. By only grafting one or two buds it reduces the energy needed to supply resources to others. When the rootstock is finally cut you should wash it as well with a spray bottle because it will only take a few seconds to begin drying out and interfering with the graft. Now join the scion and the rootstock and immediately seal with parafilm, buddy tape or some other favored grafting material. You can make sure that it is pulled together tight by wrapping the parafilm with electrical tape without covering the new buds.
When cleft grafting just make sure that your rootstock and scion diameters are identical or at least that the cambium layers are perfectly lined up on one side. Many grafters will also maintain a small amount of leafy growth on the rootstock to provide some nourishment to the new graft until it is mature enough that the growth on the rootstock may be permanently removed.
Bark grafting, or veneer grafting also works well for grafting mulberries, but it works the best when your rootstock caliper is larger than your scion. To perform this trim off the leaf below a bud on your scion wood, still leaving the petiole to be used as a handle. Then simply score the bark around the bud to be transferred in the shape of a square, and score the bark on the rootstock in the same shape. Gently lift the bark from the rootstock off and discard it, lift the bark off the scion and insert it, ensuring that the edges all match.
Tip: If your edges of your bud bark are larger in one dimension than the edges of the square you made on the rootstock, simply place the bud on the area, and trim to fit using a sharp knife. Note: Veneer, or bark grafting has a very high success rate on most plants, but is often slower to take. Be patient, but expect success.
If you time your grafting right the bud may begin to grow between 2 days to 2 weeks. If the weather is warm or sunlight is hitting the graft directly consider covering the area loosely with some aluminum foil until the fusion has taken place.
Mulberries can be grafted from late winter through summer in moderate climates. Some cultivars are difficult to graft in summer months, and here in Arizona we have a narrower window than the rest of the country. Only bark, or veneer grafting may be done in late spring or early summer. It is important to note that when grafting after the weather has begun to warm up you must keep direct sunlight away from your graft for 8-12 weeks.
Note: many varieties of mulberries may be grafted onto one tree, forming a “cocktail” mulberry tree of sorts, to extend season and flavors, however rarely are grafts successful between Morus nigra and other species. Morus rubra is also often difficult. Others may have limited compatibility or certain combinations may shorten the lifespan of the tree.
Mulberry scions should be collected during dormancy and should have two weeks in the refrigerator for maximum take. Many experts recommend grafting once buds have broken, but I have found that success is just as readily available on most varieties during late dormancy.
PROPAGATE BY CUTTINGS
Most mulberry cultivars are very easy to grow from cuttings. They may be propagated by both hardwood and softwood cuttings. Most mulberry varieties will fruit 2-3 years from rooted cuttings or if grafted onto rootstock, but some varieties like ‘Pakistan’ are so precocious that the cuttings will attempt to bloom before they have even put on roots and it will be necessary to pinch off the flowers to force the energy to go to root production.
To propagate by hardwood cuttings, take scions during dormancy that are between 3/16” to ½” diameter and about 6-10” long. You may place cuttings into the refrigerator until ready to use in a ziplock bag with a sprinkling of water.
Rooting hardwood cuttings should take place at about budbreak. Rooting hormone is highly recommended but not absolutely necessary. Push cuttings halfway down into a light well-draining potting medium such as one third peat moss, one third vermiculite, one third coarse perlite. It does not matter whether you use a pot or plastic dixie cup with some holes in the bottom for drainage. Rooting should occur in about 40-60 days. Keep the medium moist. Put a loose bag or bottle over the top of the pot for the first few weeks if needed.
To propagate by softwood cuttings, take budwood in early summer that is a ¼” in diameter or smaller and about 6-10” long with some leaves. Trim all the leaves off except one or two at the top and cut those down to 1-2” squares. You may place cuttings into the refrigerator in a ziplock bag with a sprinkling of water until ready to use.
Rooting softwood cuttings should take place in midsummer. Rooting hormone is highly recommended, but not absolutely necessary for most cuttings to take. As before, push them halfway down into a light well-draining potting medium such as one third peat moss, one third vermiculite, and one third perlite. It does not matter whether you use a pot or plastic dixie cup with some holes in the bottom for drainage. Rooting should occur in about 40-60 days. Keep the medium moist. Put a loose bag or bottle over the top of the pot for the first few weeks if needed. This method works great for Morus alba, and Morus macroura.
Once rooted begin the hardening-off process. Keep the rooted cuttings in a moist shady spot for the first week, then gradually expose them to sunlight. To make your chances of success even more solid add some rooting hormone again before planting.
Some mulberries, such as Morus nigra, are generally more difficult to root and tend to do better when grafted onto other species (though not all are compatible). If you’re going to root (Morus nigra) by cuttings there are a few things to do that will improve your odds.
First, Morus nigra bleeds too much and dehydrates quickly. Make sure to root from hardwood cuttings taken during dormancy. After planting keep it continually moist with a bucket or water jug perforated with small holes set next to the plant. Morus nigra, and morus rubra are more fastidious and will likely necessitate the use of a plastic bag covering or plastic water bottle with the bottom cut off to prevent the cutting from drying out. Red mulberries are just generally more stubborn.
Wildlife
With fruit trees come wildlife. If your trees are taller than yourself, be prepared to share with the critters. Beware of berry colored bird poop stains on your driveway, walls, or drying clothes on the line. Birds and squirrels are very much attracted to the fruit so if it is a small tree and you’re not willing to share with local wildlife you may have to resort to bird netting or holographic bird scare tape to prevent them from getting to it. The fruits are in fact so attractive to birds that many farmers will plant them in hedgerows to draw birds away from damaging crops.
Also, the animals are usually smart enough to not eat unripe fruit. You won’t want to either. It can cause a stomach ache and the milky sap is an irritant.
In the Landscape & Environment
Mulberries work wonderfully well in the landscape in the right spot. Not only are the vast majority of trees prolific fruiters, providing enough for you and the birds, but they also provide a fast-growing shade canopy while basking in the heat of the summer. They are wind tolerant and work well as a windbreak. The majority of their roots are within the top 2 feet, and they have a lot of them, and a lot of sinker/anchor roots, so it performs super as a bank stabilizer.
Some varieties can handle continuously wet soil, though not thriving there is a weakness of others. Most can tolerate temporary drought and air pollution. Even the residual toxins left in the soil by neighboring walnut trees won’t phase them, and are in fact used as a buffer between walnut trees and juglone sensitive apple trees in permaculture guilds. Fruitless cultivars are often used as street trees, though you will want to avoid that function with a fruiting one. The large leaves make for great foliage contrast in design, and make sure to consider the fall color as a feature.
Despite all of their virtues, many uncultivated seedling white and red mulberries and their hybrids can become weedy, growing quickly from seed deposited by birds in empty lots, parks, un-maintained flower beds and landscape borders. Black mulberries are not so prolific, having a narrower range of ideal climates and environments in which they thrive. They prefer warmer climates, and do not do nearly as well in locations that experience hot humid summers.
Pests and Diseases
Mulberries are generally pest free and affected by few diseases. For a list of the few that may occur, we have created a separate post on mulberry diseases here.
Harvesting and Processing
Mulberry fruits generally take 2-3 months from flower to harvest and ripen over an extended period allowing multiple harvests. Berries picked not quite at peak of ripeness will continue to ripen fully, but may not achieve the maximum Brix content that a fully tree-ripened berry will have. For cultivars that ripen to black, the fruit will be at peak ripeness when it changes from shiny to dull.
White mulberries Morus alba, Himalayan mulberry Morus macroura, and Red mulberry Morus rubra cultivars are ready for harvest in mid-to late spring, depending upon temperature. Peak productivity at harvest time will be while daytime temperatures are between 75-85 degrees. Black mulberries, Morus nigra, ripen later, usually during mid- to late-summer.
For a small hedge, espalier, or dwarf tree the picking is done easily enough by hand, or it can be shaken to collect a surprising quantity of fruit on a tarp, drop cloth, or sheet. For those who have a large tree, place a large flat sheet (that you don’t mind staining), painters cloth, or tarp underneath the tree canopy during harvest season, shake the tree or leave it laying there overnight. First thing in the morning go out and clean off the tarp. You now have a large gathering of its sweet fruit to eat with your breakfast. Those that drop throughout the day can be collected at intervals and put into the freezer for pancakes, syrups, pies, and desserts. The best quality fruit for fresh eating is harvested in the morning.
This method works best for Morus alba, Morus macroura, and Morus rubra fruit and hybrids, as they will more easily release from the tree and the flesh is firmer than that of Morus nigra, resulting in less damage from drop.
Black mulberry harvests are usually a little more labor intensive, as they will likely need to be harvested by hand to avoid damage to the fruit, which tends to be more tender in nature. The berries are juicier than those of Morus alba, Morus macroura, and Morus rubra and are easily bruised. Be prepared to be stained! The stem of Morus nigra also does not readily release from the branch until the second or third day after ripening, which allows additional harvest time, but requires harvest by hand using bonsai clippers during any time prior to that release. If done daily, harvesting only fully ripe berries may be done without the use of clippers. To ease in harvest Morus nigra trees are often more suitable for training into a low scaffold such as espaliering.
Storage
As I am sure you have noticed, you will not find mulberries in the grocery stores. They are too perishable to ship. It is recommended to eat them fresh or freeze for later use. They will keep up to two days in the refrigerator in a sealed container if not washed. Washing softens the skin further making them spoil faster.
Nutritional value
The mulberry is one of the best sources of antioxidants of any fruit consumed and is considered one of nature’s perfect superfoods. Not only is the mulberry an excellent digestive aid, it is also a great source of energy (as a prebiotic). They can improve metabolism, increase circulation, improve eyesight, boost immune system, help lower cholesterol, aid in weight loss, prevent some cancers, and ultimately slow down the aging process substantially. The fruit contains iron, riboflavin, vitamin C, vitamin K, potassium, phosphorus, calcium, substantial fiber, and many phytonutrients. And as if it has not already earned itself a place at the table, it can also help lower blood sugar.
Uses
Best eaten fresh, as the high sugar content and tender fruit skin promotes quick oxidation, fermentation, and spoilage. Excellent frozen on the day of harvest to be used later in sherbet, icecream, jams, jellies, wine, pies, pastries, syrups, and other delicious confections. The fruits maintain their shape better for pies if they are used slightly unripe. Morus nigra may be used as a substitute for blackberries in any such recipes. Light colored berries pair well with apples, pears, and quince in recipes and are often sweeter without the complexity of flavor of the darker berries. Mulberries are often dried and crushed to use as a sugar substitute in the Middle-East. Mulberry leaves are an excellent substitute for grape leaves in recipes such as dolmas.
Cultivars
If you live in areas where you can grown all mulberries, by planting a variety you can be rest assured that you will have berries from spring through summer. Morus alba and Morus macroura mulberry cultivars and hybrids will satisfy your early season berry needs, Morus Rubra provides you with mid-season production, and Morus nigra mulberry varieties will most assuredly provide you with exceptional tasting fruit from mid to late summer. Black mulberry cultivars are considered the best tasting berries of all time by many, but the berries are a little more difficult to harvest due to their having a more delicate skin, collapsing when squeezed during harvest. Morus alba and Morus rubra varieties tend to release easily from the tree and have a sufficiently tough skin, but Morus nigra types have a stronger attachment.
Morus nigra types supposedly cannot hybridize with other mulberry species because it has 308, instead of 28, chromosomes in its genome. All hybrids are between other species, though there is rumor that a nurseryman in Belgium has successfully hybridized Morus nigra with Morus kagayame, Morus macroura, and Morus laevigata. More investigation is needed to confirm this.
Important note: Mulberries are often sold under incorrect names. Most of the time, I do not venture to think that nurseries are intentionally trying to cheat their customers, rather, I believe it is a result of ignorance. It is always best if you get a chance to sample the fruit of the tree that is being sold to determine that it is what you want. For example ‘Dwarf Everbearing’ and ‘Gerardi Dwarf’ (Morus alba) are often sold as “Black Mulberry”, sometimes even labeled Morus nigra!
Another important note: Flavor varies greatly in soil type and climate conditions. An excellent tasting fruit in California, may not be so excellent in Florida, and visa versa. Another good reason to attend taste tests offered by the nursery selling the trees if possible.
By carefully selecting the varieties you want (grafted onto different rootstocks if necessary) you may be able to provide yourself with tree-borne berries all summer long. The following are a few popular cultivars. This is by no means a comprehensive list and we have not yet tried them all, so feel free to let us know what your favorites are!
‘Oscar’
Morus alba x Morus rubra. Introduced by naturalist Oscar Clark. Self-fruitful. Reddish-black, staining fruit is about 1-¼” long by ½” wide. Performs best in USDA hardiness zones 6-9. Fast growing tree to 35’ tall and wide. Very good complex flavor is preferred over ‘Pakistan’ by many. We do like this one a lot!
‘World’s Best’ / ‘Eden’s Dwarf’
Morus alba. Originated in China, introduced publicly by Bryce Garling. Black berry up to 2” long, fast growing tree grows 12-15’, but may be kept much smaller. Late freezes may be problematic. So easy, and loves the heat!
‘Four Seasons’
Found in northern Taiwan in 1957. Known commercially as 46C019. Currently the most widely planted genotype in Taiwan. Tree is dwarf 12-15’, but may be kept smaller with light summer tip pruning. Berries are black, medium to large size with medium sweetness and complex flavor. Production is prolonged- known to fruit all summer long.
‘Persian’
Morus. nigra. Self fruitful. Black fruit is 1-¼” long and an inch wide. Juicy with a rich, subacid berry flavor. The fully ripe berry is considered to taste like every desirable berry species combined together. Considered drought tolerant once established. Strongly staining. Slow growing to 30′ tall. Handles higher pH soil better than many other mulberries. I have gotten to taste this one on an old flood irrigated farm in Queen Creek, AZ. The flavor was amazing.
‘Collier’
Morus alba X Morus rubra. Purplish-black fruit 1-1/8 inches long and 3/8 inch in diameter. Sweet flavor with just a trace of tartness. The quality is considered very good, on par with Illinois Everbearing. This tree has an extended ripening and harvest season. Medium sized spreading tree that is relatively hardy and very productive.
‘Downing’
Morus alba var. multicaulis was a seedling sown in 1846. The fruit is black with excellent flavor and ripens from June to September. Unfortunately the name has been contaminated and other varieties have subsequently been sold under the same name.
‘Illinois Everbearing’
M. alba X M. rubra. Originated in White County, Illinois. Introduced to the market in 1958. Black fruit is nearly seedless, large and long, averaging 12 berries per ounce. Flavor is rated good to very good and very sweet. Matures over a long season. The tree is vigorous and semi-dwarfed, extremely hardy and very productive. Still considered the best by many. For me the flavor of Illinois Everbearing is similar to Oscar.
‘Kaester’
Morus nigra. Originated in Los Angeles. Introduced to the market in 1971 by Nelson Westree. Black or deep purple, large and elongated fruit, 1-1/2 inches long and 1/2 inch in diameter. The flavor is very sweet with a good sweet/tart balance. Tree bears heavily.
‘Pakistan’
Probably Morus macroura, possibly hybridized with Morus alba. Originated in Islamabad, Pakistan. It is self fruitful and non-staining. Very large ruby-red to dark purple-black fruit from 2-½”, up to 4” long and ⅜” in diameter. The fruit is firmer than most cultivars and less juicy. Sweet with a good balance of flavors resembling a cross between raspberry and grape, exact flavor dependent upon climate and soil terroir. The quality is excellent. Fruit development is dependent upon root length and health more than other cultivars. Because of this it is not uncommon for fruit to not ripen the first year and drop most of them early. By its third year, the fruit will remain on the tree until fully ripe and delicious. Because it is loosely attached, the large fruit can be blown off the tree by a strong wind before it is evenly ripe. This tree grows 25-35′ high. It thrives in warmer zones in the Deep South, and mild winter areas such as southern California and the low desert region of Arizona, but often performs well enough in cooler regions.It is branch hardy to 25°F. The tree is large and spreading with large heart-shaped leaves. This is definitely one of our favorites!
‘White Pakistan’ / ‘King White’/ ‘White Shahtoot’
Morus macroura. A non-staining, white phenotype up to 4″ long, less juicy, with a sweet honey-like flavor. It grows in USDA zones 8b-10 and to 25-35′ high. There are several white Morus macroura varieties. For a sweet tooth like me, I find them all irresistible. They are the sweetest of all the mulberries that I have tasted.
‘Australian Green’
Morus macroura. This cultivar is a variation whose taste apparently resembles honeydew melon.
‘Dwarf Red Shahtoot’
Morus macroura. Originated in Australia. This dwarf red fruited variety may be easily kept as an espalier or small tree to 12’.
‘Riviera’
Morus alba. Originated in Vista, Calif. Purple-black fruits, 1 to 1-1/2 inches in length, 1/2 inch in diameter. Flesh somewhat juicy and very sweet. Very good dessert quality. Ripens over a long period, from April to June.
‘Russian’ (Tatarica)
One of the oldest cultivars still in propagation. Introduced into Europe from China about 1,500 years ago. Fruit is reddish-black and of good quality when ripe. The tree is bushy and grows up to 35 ft. tall. It is very hardy and drought resistant. Planted widely for windbreaks and hedgerows.
‘Shangri-La’
Morus alba x Morus rubra. Originated in Naples, Florida. Self fruitful with a complex sweet-tart flavor that has become a popular favorite. Produces staining, 1-½” long, black fruit. Good disease resistant mulberry for the Deep South, growing 25′ high in USDA zones 6-10. However, this cultivar is an early bloomer and will often lose fruit or branches when late frosts occur in the colder regions of its range. This may have something to do with the fact that this variety doesn’t seem quite as productive in Arizona as some other varieties. The tree has huge heart-shaped leaves. I love these fruits a bit better than ‘Pakistan’, but my conditions haven’t been as ideal and I haven’t seen these trees produce as much.
‘Tehama’ (Giant White)
Originated in Tehama County, Calif. Very large, white-colored fruit 2-¾” in length and ½” wide. Very sweet, “melting” flesh. This large-leaved tree has a beautiful form. Best adapted to mild winter areas. Produces some male flowers the first few years and eventually becomes fully parthenocarpic.
‘Wellington’
Originated in Geneva, New York. Reddish-black medium-sized fruit, 1-¼” long, ⅜” in diameter. Many berries are long and slender. Berry is very soft, but has a good flavor. Ripens over a period of several weeks. ‘Wellington’ is a heavy producer. Speculation exists that this variety may be the old cultivar ‘New American’, which was also sold many years ago as ‘Downing’.
‘White Persian’
Morus nigra. This is an unusual self-fruitful, and non-staining white fruiting phenotype of the black mulberry. Fruit measures up to 1-¼”, and is possibly the best tasting of the white fruited mulberries.
‘Dwarf Black’
A self-fruitful dwarf cultivar of Morus nigra, with strongly staining, small black berries, varying in size between 1/4″ to 1/2″ long, with an excellent sweet berry flavor. It produces both a spring and a fall crop, gradually increasing production over several years. The small berries are tedious to harvest, however, and are a bird magnet resulting in purple staining bird poop everywhere. The tree is rather slow growing up to 8-12′ high. USDA hardiness zones vary according to rootstock, either 5-11 or 7-11. A cultivar named ‘Black Beauty’ doesn’t seem to express much difference in berry size. Dwarf Black Mulberries do well in large containers.
‘Dwarf Everbearing’
Morus alba. Self fruitful. Heavy producer of strongly red-staining, small black berries. It grows 8-12′ high. USDA zones 5-11. This tree is often used as a rootstock to dwarf other M. alba trees, but is highly susceptible to root knot nematodes. This tree is often misrepresented as Morus nigra.
These have always been very abundant for us except when we have had root knot nematodes. The berries are tasty, albeit a bit fiddly to harvest (good for kids and chickens). Although the tarps-and-bowls-below-and-shake method works well for this one.
White Fruiting Mulberry
Morus alba. Self-fruitful. Non-staining, white colored berries up to 1″ long, are mild and sweet, and taste like mild honey mixed with melon or white peach. It grows to 30′ high. ‘Lavender’ is a pink to light purple-tinged variation, though birds are not as readily attracted to the white mulberry fruits. White mulberries tend to conserve the majority of their sweetness during dehydration.
‘Weeping Mulberry’ / ‘Pendula’
Morus alba hybrid. Not self-fruitful, staining, reddish-black. Fruit is relatively poor-tasting. Primarily grown as an ornamental from 8-15′ high and wide. I have tasted fruit of several trees. Fruit quality is inconsistent, some good, some taste green even when ripe.
Conclusion
Mulberry trees are very easy to grow and tolerate a wide range of soils and climates. Many modern varieties are self-fertile and still produce copious amounts of delicious, seedless fruit without the need for pollen. Some varieties have a long production season.
Pakistan and other M. macroura hybrids come off the tree easily for harvest, but are also blown off the tree easily in spring winds. Morus nigra are excellent options in regions where winds may be a concern. The fruit is kept fresh on the tree until several days after initial ripening, allowing harvest time.
They produce wonderful summer shade, but are also decidedly deciduous, allowing sun penetration and warming in the winter. An ideal location would be far enough away from potentially damaged concrete walls, walks, and from water lines, sewer lines, and septic systems.
Choose for flavor, or choose for non-staining berries. Keep away from sidewalks and driveways to prevent the extra mess of sticky berries. Birds love them as much as people and may spread seeds and purple poop everywhere. White fruiting types and some cultivars such as ‘Pakistan’ and ‘White King’ will not stain.
“Fruitless” mulberries produce pollen and should be avoided by people with allergies and in areas where allergies are especially a concern. Many municipalities erroneously ban the sale of all mulberries as “pollen producers”.
Morus alba and Morus macroura are used in the raising of silkworms, but they will not eat the leaves of Morus nigra. Morus alba has naturalized in much of North America and easily hybridizes with Morus rubra. Morus nigra is found occurring naturally in only a few states.
Regardless of what kind of mulberry you decide to grow, the shade, the lush greenery, and the amazing fruit are all worth the small amount of effort they require. You can’t get much better than a plant that is tasty, nutritious, AND so easy to grow. I hope you have fun designing your edible paradise and do let me know if you manage to find space for a delicious mulberry in your dreamscape!
~Jason Tibbetts
Edible Landscape Artist, Educator, Designer, and Coach
Mulberries are generally pest free and affected by few diseases. For a list of the few that may occur, we have created this short post on mulberry diseases.
Symptoms of stem canker generally are most evident in cuttings that appeared to take and then subsequently died. The new shoots suddenly shrivel and die. When the cuttings are removed from the soil it is apparent that the bark is rotting and peeling away below the soil. Black mycelial threads may be seen under peeling bark. In commercial applications cuttings are most often taken dormant and pre-treated with carbendazim to prevent infection.
LEAF RUST
Cerotelium fici, Aecidium mori
Symptoms of leaf rust include small brown irregular shaped red or rust-colored spots appearing on older leaves underside. The leaves subsequently turn yellow and wither prematurely. Otherwise it may not harm the tree. Often exacerbated by lack of air flow between plants; planting out further apart reduces spreading. The problem may subside on its own. In commercial culture plants are sprayed with carbendazim.
LEAF SPOT
Cercospora moricola
Symptoms of leaf spot begin as circular spots on leaves that become larger and irregular in shape and eventually coalesce and form shot holes in the leaves. Severely affected leaves yellow and drop prematurely. Most common commercial control of leaf spot is through the use of carbendazim.
POWDERY MILDEW
Phyllactinia corylea
Powdery mildew is an ectophytic (lives outside of, and on the surface of its host) fungus that appears first as a powdery white (mycelial) film in spots on the undersides of leaves that spreads until it covers the entire leaf. The leaf will then begin to thin, curl, yellow, then brown and drop off.
Disease is most common in the low desert after spring rains where the humidity is greater than 70%, the temperatures are hovering between 75-80° F degrees, there is limited air circulation, and a low pH on the leaf surface. Thrives in shadier environments, such as on the north side of a building or under the canopy of another tree.
Commercial chemical control includes the use of carbendazim and other fungicides. Cultural control measures include ensuring more air circulation between plants, thin trees to increase sun exposure. Some commercial varieties grown for silk production have been tested for resistance. Home treatments include sprays that raise surface pH to levels that the mycelium cannot survive: common home remedies include milk sprays or baking soda sprays. Lady bugs will also feed on mildew fungus.
FALSE MILDEW
Mycosphaerella mori
False mildew is similar to powdery mildew. It appears as a web-like film on the mulberry leaves. To eradicate this disease, spray trees with a fungicide at the first appearance of the fungus. Again, simple surface pH treatments may prove effective. Remove leaf litter to prevent reinfection.
BACTERIAL BLIGHT
Psuedomonas syringae
This particular bacteria plays some fascinating roles in the environment. While it is a bacteria that can be highly pathogenic, in most healthy environments it causes little to no issue. It is highly hydrophilic and nucleizes ice crystals in warmer than freezing temperatures in the atmosphere creating rain clouds.
As a pathogen however it can cause serious damage. Infection manifests as black spots on the leaves and large brown spots on the fruit. Flowers, fruits, catkins, and branches may shrivel and die. Leaf veins may take on an unnatural dark color. At mature stages of infection cankers can appear on the branches and trunk. Infected areas may ooze moisture in wetter environments. This bacteria becomes problematic in areas where foliage is regularly damp or moist and there is poor air circulation. It is most commonly seen after rain with prolonged periods without dry-out.
Because the bacteria takes different forms and some are more pathogenic than others, Infected branches, leaves, and fruits should be removed and burned or bagged and discarded in municipal waste. If the trunk does develop cankers it should be removed before allowed to fully die. This will ensure that the bacteria does not end up contaminating the soil in populations that are more difficult to manage.
This bacteria needs to feed inside damaged plant tissues in order to propagate. One strategy it has for survival is to raise the freezing temperature on the leaf surface allowing freeze damage to occur at temperatures as high as 46° F! While the bacteria exists on every continent in the world, it has highest concentrations in tropical regions. Management of the disease is done by thinning and improving air circulation in the canopy of the tree. Limit moisture on leaves as much as possible.
Pseudomonas mori
Symptoms of bacterial blight caused by Pseudomonas mori appear as irregular patches on the undersides of the leaf that appear soaked. Leaves curl, turn brown to black, and rot. Black lesions appear running lengthwise down new shoots. Leaves turn yellow and drop prematurely. Unfortunately, this species of bacteria is a little more malign than P. syringae and the best management practice is uprooting and burning the plant, and exposing the soil to air circulation. Commercial treatment includes the use of the chemical Streptomycin or Streptocycline.
ROOT KNOT NEMATODES
Meloidogyne incognita
Root knot nematode infestation is not usually immediately apparent. The plant grows slower and stunted, and leaves may appear smaller. Leaves turn yellowish and the edges begin to dry up and turn brown. The entire plant may wilt, and flower and fruit production is severely affected. The plant’s failure to thrive may be attributed to several other things by observation before an accurate diagnosis is achieved through root examination.
The roots of a tree infected with root knot nematodes are quite another story. They exhibit characteristic galls, knots, and twisting. Roots may be stunted as well and show areas where the root is split open like a baked potato.
Root knot nematode is common in sandy soils with a good loam humus that remains a little on the dry side. Commercial control is often done by deep ploughing in summer and applying Carbofuran 3G. Other control measures include amending the soil with neem cake, or applying beneficial predatory nematodes on a regular basis. This is the preferred organic treatment. Evidence of success with this method is apparent when comparing initial infestation with root knot nematode population 3 years later.
ROOT ROT
Macrophomina phaseolina
Symptoms of root rot include sudden wilting and withering of leaves. Plants affected by root rot fail to sprout after pruning and subsequently dry up. Both the primary and secondary roots rot, resulting in plants that can be uprooted easily. Roots turn black and root bark is decaying. Control measures primarily consist of uprooting and burning the entire plant and its roots. Allow churned soil to fully dehydrate. Apply neem cake and Bacillus subtilis at recommended doses. In isolated pot culture where mycorrhizae will not be encouraged application of Trichoderma viride will also provide substantial benefit. Commercial treatment includes a soil drench of carbendazim at recommended doses.
MULBERRY LEAF SPOT
Cercospora moricola
Symptoms of mulberry leaf spot include yellowing foliage accompanied by dark spots. Most often seen on the fruitless male selection available at most nurseries. Trees will generally survive without a fungicide treatment, however prevention is entirely possible by thoroughly cleaning up all fallen leaves.
Texas Root Rot, or Cotton Root Rot, which is commonly seen in the Southern United States, is a very serious condition. Most flowering trees are susceptible to this disease to some degree or another. Monocots such as dates and bananas are immune, and trees that excrete powerful root exudates such as pecans, pomegranates, citrus, and guavas are often observably more protected. Desert native trees are highly resistant.
It is most often observed in Summer when leaves of many species will wilt and dry on the tree in a matter of days. By the time it is observable the fungus has already spread throughout the entire plant’s vascular system. Uncommonly, the tree may live for a year. Mulberries appear to be less susceptible than some other species, though still affected.
The infecting fungus prefers tight clay soils of a high pH, that remain moist for long periods of time. The disease is spread as new roots come in contact with fungal material in the soil or old decaying infected roots. Chinese Evergreen Elms of 6-8 years in the ground are particularly sensitive to this disease. Since these trees are ubiquitous in the desert southwestern landscape plant palette I have learned to look for neighborhoods that have a high number of elm trees that are 8” in diameter or larger. These neighborhoods may be relatively free of the soil-borne fungus.
There is no cure for Texas Root Rot. Avoid contracting this fungus by avoiding the use of fertilizers high in nitrogen, as these may reduce the tree’s microbial disease protection network. Some mitigation measures exist, such as air drying soil, improving percolation, lowering pH by adding sulfur products. As soon as symptoms are observed, contact an arborist to schedule a consultation, as this disease can spread to the surrounding plants and trees. Official diagnosis can only be obtained by lab results, but some areas are particularly prone and arborists will know what they are looking for. Avoid replanting susceptible species in the same location.
ARMILLARIA ROOT ROT
Armillaria mellea
Armillaria root rot, known more often as oak root fungus or shoestring disease, can infect mulberry trees. Most of the rot infection will occur underground and internally, heartwood and roots are where the majority of the damage happens. The foliage will be diminutive, leaves may yellow or brown and drop prematurely. Top branches or limbs will be weak and die progressively down from the canopy. Red or brown mushrooms may appear at the base of the trunk or on surface roots.
SOOTY CANKER
Hendersonula toruloidea
Sooty canker is a common fungal disease that affects many species of plants, including mulberries. The disease is particularly prone during stress (sunburn resulting from over pruning is a big one), or after pruning, as spores enter exposed cambium tissue. The fungus sets in during the winter, but evidence is most apparent during the summer when discolored wet spots appear on the branches. Canker wounds appear on the branches and trunk. Leaves wilt and die back. Bark splits and may easily peel off the tree in paper thin strips, exposing a black powdery layer of spores. The mold will continue to spread, often taking several years to kill the tree.
If caught early it may be treatable. Prune off all infected branches, carefully disinfecting each cut with an alcohol or bleach solution. Paint areas with a fungicide or antibacterial mouthwash. Make sure that watering and fertilizing is consistent, but not overdone and that the tree is not stressed.
POPCORN DISEASE
Ciboria carunculoides,
Popcorn disease is a fungus-caused deformity of mulberry fruits that most commonly occurs in the southern United States, in which the individual carpels of the fruits swell to resemble unpopped kernels of corn and usually results in dry texture and drastically reduced palatability of fruits that manage to remain. Morus alba hybrids are particularly prone to this condition, but Morus rubra may occasionally exhibit infection as well. The disease carries on from one season to the next, so collecting and burning all infected and fallen fruits or sealing in bags and disposing of them in municipal waste collection will largely help control it, but the ripe fruit is still sufficiently attractive to birds, and so it may spread via that means. Even with cultural control measures of manually removing infected fruit, a hose-end spray application of Bordeaux fungicide, or Monterey Disease Control may still be necessary as a second line of defense. Unfortunately, weather and environmental conditions are factors and some years may be worse than others.
OTHERS
Other pathogens and pests that may bother mulberries and their fruits are – Cylinderosporiasis, curly-leaf viruses, thrips, beetles, mulberry barbel, wireworm, spider mites, mealy bugs, and various caterpillars including mulberry moths.
Scientists are discovering the link between happiness and dirt. That’s right, getting your hands into some dirt can mean more happiness. Why? Well, apparently there’s a little critter in the dirt known as Mycobacterium vaccae that has similar effects on the human brain as Prozac and other pharmaceuticals but without the negative side effects and chemical dependency. This little bacterium stimulates serotonin production which helps to decrease agitation, anxiety and increase overall happiness.
Huh! So, for thousands of years, humans have been domesticating and planting crops, digging wells and canals, digging for minerals, digging to catch animals, digging to make shelters, roads, fields, and fence posts, digging, digging, digging. It’s no wonder that our human habits of churning the earth’s crust have continued unabated into our modern era despite all of our newly developed technology and sophistication!
As a bonus, the effect of the bacteria not only lowers stress and improves mood and vitality, but cognitive function and concentration is improved as well.
It gets better! M vaccae has demonstrated anti-mutagenic properties useful in preventing cancer, rheumatoid arthritis and Crohn’s disease, and in boosting our immune system. Dirt particles may come in direct contact with the blood stream through a cut or abrasion during gardening activities. The means of absorbing the bacteria may or may not matter, but the effects of the contact may last up to three weeks! The testimony that the act of gardening does relieve stress is true – no surprise for some of us.
My kids (at the time of this writing ages 5, 3, and 1) recently went to visit their Nanna, Granddad and cousins. Long-term landscape construction resulted in a huge, unavoidable, glorious mound of soil piled in the front yard. There was even a muddy spot next door where a small tree had been removed. My kids played in the dirt and mud and, soon enough, pure filthiness ensued. They discovered that if you pack the dirt just right, you can scoot yourself from the top of the mound to the bottom, face first, as if on the world’s greatest slide. There was dirt in hair, mouths, and little jean pockets.
So, take some advice from my kids. If you want to be happy, make sure to get in a healthy dose of dirt before your bath!
~Jason Tibbetts
References:
Grant, B. L. (2017, March 27). Soil Microbes And Human Health – Learn About The Natural Antidepressant In Soil. Retrieved February 11, 2018, from https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/antidepressant-microbes-soil.htm
Sweet potatoes have been around for centuries. Domesticated sweet potatoes were present in Central and South America more than 5000 years ago. People obviously liked them and shared the bounty with others because now they are found all over the world including the continents of Africa, Asia, Europe, and Australia. The first Europeans to taste sweet potato were some of the members of Columbus’s expedition when they landed in Haiti in 1492. Now, most of the world can enjoy this sweet tasty versatile food in their kitchen, and garden.
We first discovered the joys of growing sweet potato plants a year after we got married. Marin had just returned to Arizona from New York missing the greenery and ivy that grew wild there. The hottest part of an Arizona summer was just beginning, and not a season of weather we generally look forward to.
That May we plunked a leftover piece of a purple sweet potato in the ground. We put it right under the eves of the house not far from where the A/C unit left a constant condensation drip. Most plants this time of year wilt no matter how much water you give them and seem as if they will turn to dust if you touch them. But for this sweet potato, in the miserable summer heat, oh joy of joys! It thrived and quickly became a lush groundcover reminiscent of the ivy Marin so fondly remembered in New York! It took off and filled that entire border area so well that we had to trim it back drastically every time we mowed the lawn!
We have learned much about growing and using sweet potatoes since then and now we highly recommend this incredible plant for anyone who is growing an edible landscape! Not only are the tubers tasty and colorful and the greenery beautiful, but it is a two-for-one crop. Sweet potato leaves taste great too!
SWEET POTATO OR YAM?
This topic usually needs some clarification. The many different types of “Sweet potatoes” and “yams” found in markets in the continental United States are generally the same species, Ipomoea batatas. “Batatas” is the name that the native people in Haiti called them when Columbus arrived. The Spanish later changed the name to Patatas, and then when introduced to the common potato, they also called that patatas. Now we call them sweet potatoes because they resemble a potato, but the Ipomoea was there first!
Here’s where the names “sweet potato” and “yam” gets confusing. The tubers that we eat may be classified by their two different characteristics of texture when cooked. These two distinctions are those that become moist-and-sweet when cooked, and those that remain somewhat dry and flaky (resulting in different ideal uses in the kitchen). Some varieties are able to convert more starch to sugar during cooking and will be more moist and sweet. These are often marketed as “yams” while the varieties that are comparatively drier and starchier are usually differentiated as “sweet potatoes”. Unfortunately, that doesn’t always apply and they may be marketed with interchangeable classification. Generally, the drier ones are not as readily available to home gardeners and are less common in markets due to less popularity, giving rise to markets using the appellations “yams” and “sweet potatoes” more fluidly.
To complicate matters, “true yams” of the genus Dioscorea are often sold in international markets in bins right next to bins full of Ipomoea sweet potatoes and yams. Sometimes they go by the name “yams” and other times they go by “ñame”, the common name of yams in many Latin American countries. Another species of Dioscorea is called “yamaimo”, or “Chinese yam”, one of the varieties of Dioscorea from China or Japan. Occasionally there are other Dioscorea species available as well, but as true yams are a very interesting topic, we will save that discussion for another post. True yams are generally not as sweet as Ipomoea cultivars, which is why the differentiation “yam” can be so very frustrating. Note: while the leaves of sweet potatoes are edible and delicious (as will be discussed later), the leaves of most Dioscorea species are toxic, and even fewer of the tubers are safe to eat raw.
CHOOSE IT:
RELATIVES
In addition to the sweet potatoes that we are familiar with, the genus Ipomoea also contains several perennial wild types and relatives globally. Upon inspection, you will see that they all bear the signature flower of the common garden morning glory and moonflower, which are members of the genus though generally not considered edible without extensive preparation. In North America, there are a few that can get quite large (known colloquially as “manroot”) and are supposedly best when the roots are carrot size. One such is Ipomoea pandurata known by some indigenous American peoples as “mecha-meck”, and another is I. leptophylla. I. aquatica, also known as “kang kong” or “water spinach”, is invasive, and in some places illegal, aquatic species grown in Asian communities for its delicious greens. There are many other edible and medicinal species of Ipomoea around the world including I. mauritiana, I. costata, I. simplex, and others. Identification and methods for processing Ipomoea vary according to species and we will not go into detail here.
Ipomoea batatas, our common tetraploid sweet potato, only exists as we know it in cultivation. While not particularly cold hardy, in theory, it could potentially be crossed with some of its cold-tolerant wild relatives such as I. pandurata. Worldwide there are somewhere between 6500-7000 different varieties of the familiar domesticated sweet potatoes, with new ones coming out all the time. In the United States, there are roughly 100 popular ones. Here are some of the more common sweet potatoes that we have grown.
NOTABLE CULTIVARS:
‘All Purple’ (120 Days to harvest); Dark purple flesh with purple skin. Hardier than most. A fast and strong Grower (deep and long brittle roots may need containing). Roots are dry and starchy, slightly sweet, and store well. Best tubers are grown from slips. Will become fibrous and inedible if left in the ground too long.
‘Beauregard’ (90 days to harvest); Orange flesh with red-orange skin. Vigorous vines. The early-maturing variety produces high yields.
‘Centennial’ (100 days to harvest); Orange flesh with copper skin. Fine-grained. Early. Semi-bush vines produce tapered roots. A commercial standard in U.S. High yields and a good keeper. Performs well in clay soils.
‘Georgia Jet’ (90 days to harvest); Deep orange flesh with red skin. Moist. Very fast-growing semi-bush type.Early producer.
‘Ginseng’ (120 Days to harvest); Orange flesh with pale orange skin. Vigorous semi-bush vines. Prolific producer. Dry, but sweet. Distinctively lobed “trident” shaped leaves.
‘Hernandez’ (120 days to harvest); Orange flesh with light red skin. Reddish-purple-stemmed. High yields from vigorous vines may produce some “football-sized” tubers in each bunch. Mid-season. Very sweet and moist when cooked. Great baking potato.
‘Jewel’ (100 days to harvest); Orange flesh with copper skin. Moist. Vigorous semi-bush vines produce uniform roots that are good keepers. Mid-season.
‘Red Japanese’ (95 days); White flesh, with red skin. Dry but sweet. Popular in Asian markets. Vines of average vigor are disease resistant. Heavy producer (if watered well). Midseason. Cultivars we want to try:
‘Okinawa Purple’ Deep purple flesh with light beige skin. Slow vines. Very late.
‘Okinawan’ Purple flesh with pale purple skin. Slow vines. Very late.
‘O’Henry’ (100 days); White flesh with white skin. Sweet and creamy. Short busy vines. Early producer. Heirloom.
‘Porto Rico Bush’ (110 days); Copper skin covers sweet, moist, Deep orange flesh with copper skin. Moist. Compact bushy vines.
‘Vardaman’ (110 days); Deep red-orange flesh with yellow skin. Bush variety with burgundy-bronze new foliage. Midseason.
‘White Hayman’ (100 Days); White flesh with cream skin. The flesh is starchy and sweet and turns more yellow when cooked. A good substitute for “Irish Potatoes,” but with a sweeter flavor. Vigorous vines produce large uniform roots. Midseason. Heirloom.
New foliage of ‘Japanese Red’ sweet potato vine
Sweet potatoes come in many different foliage colors and textures. All ornamental varieties that can be purchased from your local garden center will have edible and nutritious leaves, which is why they are perfect for an edible landscape! (though very few will produce a tuber and even fewer that do will prove palatable). We often see the purple leaves next to the chartreuse green leaves that make a perfect pop. All are edible, but some are sold for their glamorous foliage, others for their tasty roots, and still others are cultivated specifically for their tender, flavorful greens.
PLANT IT:
SOIL PREPARATION
One of the most important things to consider when planting sweet potatoes is that they require a loose and “roomy” soil 8-12” deep to grow good tubers. Fail to provide this, and other aspects of planting and soil preparation will matter little, as your tubers will be no bigger, and of no more culinary value, than a doorstop.
PROPAGATION METHODS
The most common method of propagation is by “slips”. Slips are vegetative shoots that come from the tuber itself. These can be obtained by rooting a tuber, or a piece of the tuber, in a jar of water using toothpicks to suspend it partially submerged in the water. Keep the water fresh. The new shoots that result within a few weeks in a sunny windowsill or under a grow light can then be removed, and themselves rooted in water. Good slips will have sturdy, thick stems, be 6 to 9 inches long, and have at least 5 leaves. One medium-sized sweet potato should yield about 12-20 good slips.
Within a few days of placing slips in water, they will have inch long roots and will be ready to plant. These will have the highest likelihood of forming beautiful spuds. In areas with a long growing season, such as ours, you can also remove shoots from an actively growing plant and root them in water for transplant, though some sources say that the resulting tubers may be more fibrous- I have not noticed. Whichever method you choose, lay the sprigs sideways an inch or two under the surface 18” apart and top with compost and organic mulch.
I have also simply placed a sweet potato in a brown paper bag on the back porch in late April until it sprouted and then planted it. Tubers still result and it’s less effort!
PLANTING SEASON
The best time of year to plant sweet potatoes in our area is March to June, usually whenever you would also be planting okra. They both love that heat!
GROW IT:
MICROCLIMATES
Sweet potatoes are a tropical vegetable and appreciate the long, hot, humid summers. When it’s too hot for me and most of my garden, sweet potatoes thrive. The ideal location for growing thriving sweet potatoes is a position in the all-day open sun, though they can grow (with smaller tubers) in locations that receive a partial day’s shade. While sweet potatoes do not prefer reflected heat, most varieties can take it, as long as they have sufficient water.
COMPANION PLANTING
We have found in our own gardening experience that they make good companion plants for our banana trees, as they have the ability to shade the soil and improve fertility in the surrounding bed. They would also work well as a companion plant for ginger, canna lily, lemongrass, garlic chives and any other complimentary strap-like foliage that can hold up to the groundcover’s desire to “cover” its companions.
LANDSCAPE USES
Sweet potatoes make a marvelous summer ground cover to shield, protect, and nourish the soil. They look great covering a sloping mound, or greenery butting up against a lawn or a walk. Every container for effective curb appeal must have 3 features: a “thriller” in the center to catch the eye and provide a focal point, a “filler” to buffer the base and provide additional color, and a “spiller” to give the pot a skirt of foliage; a wall of greenery. In a sunny spot or hanging over a wall, sweet potatoes fill this function with stunning excellence. You may even be graced with some of the gorgeous morning-glory flowers late in the season.
As part of their effectiveness as a cover crop, they have also been found to have an allelopathic relationship against certain weed species. Of particular mention is their skill at making the soil environment less suitable for yellow nutsedge, an annoying perennial weed in warm weather climates that is very difficult to eradicate in cultivated and uncultivated areas alike.
Because sweet potatoes are a water and nutrient storage organ for the plant, they form as the long days wane and require regular watering for sizeable tubers. The plant is, however, fairly drought tolerant and will survive periods with little moisture, though the tubers may be of poorer quality. Sweet potatoes will produce the best tubers if they are watered regularly, starting with daily dosages the first week after planting and slowly weaning back the quantity throughout the season, while still maintaining consistency. Make sure that the watering is deep during hot, dry periods for best tubers. However, if plants receive too much water late in the season many varieties will crack and attract pests such as earwigs and woodlice, which will cause further damage to your tuber crop. The resulting tubers look more like garden goblins than those smooth sweet potatoes that you buy in the store. The trick is to find that balance.
FEEDING
While fertilization during the active growing season is not generally necessary because of its nature as a biodynamic nutrient accumulator, it is essential to start with a soil that has good tilth and have some level of organics and phosphorous. For extra vigorous plants, you may consider an occasional application of compost tea or liquid organic fertilizer as a foliar feed after the plants have been in the ground for a month or so. Be conservative, as too much nitrogen will result in excessive growth that will be a prime target for pests such as flea beetles, aphids, caterpillars, and crickets. While this largely doesn’t affect your tubers, if you are also planning to make meals out of the leafy vegetable part, this may present a problem. In short, feeding is helpful, but not too much!
MAINTENANCE
Pruning should be moderate. If you find that the plant is escaping its bed and traversing areas you would rather it not, simply pick up the vines and throw them back into the bed. By evening the leaves will likely reorient and you may not even be able to tell what you did.
MULCHING
We have found that a 2-3” layer of wood chips works wonders as a surface mulch for this plant. The chips keep the moisture in and evenly distributed while simultaneously providing a slow feeding as they break down. It is valuable to have a buffer layer of compost under the wood-chips to ensure that the plants are not starved of nitrogen. The added bonus is that the tubers form near the top of the soil just under the chips. Simply reach down under the mulch and pull up a tater for lunch (although it won’t have been cured yet)! This is an ideal way to maintain the aesthetics of the groundcover in the landscape and still get a harvest. The other advantage of this is that it prevents the vines from rooting in as they go across the ground. Instead of getting a million tiny tubers, the energy is spent on the tubers you will be harvesting.
HARVEST IT:
WHEN TO HARVEST
Sweet potatoes take about three to four months to reach maturity. Know your variety- If you let them go too long they may start to get tough or invite pests, but they are usually ok to leave until the first light fall frost. You can begin harvesting them as soon as they are big enough for a meal. Usually, sweet potatoes are ready to harvest when the leaves and ends of the vines begin to yellow. Some of the late-season varieties are best harvested after the first frost has turned the leaves black. If you are harvesting late, dig them out and leave them to sit on the ground with the dirt on them for another couple of cold nights to improve the flavor. This practice will depend upon the variety.
HOW TO HARVEST
Start by cutting the vines back to a six-inch shrub. This allows you room to work and a landmark for your digging. Most varieties will be found 4-6 inches deep in the soil with some vigorous varieties (like the ‘All Purple’) found deeper. If the tubers were grown in a raised bed or hilled they may be easier to dig out. Use a spading fork or broadfork to avoid the common mistake of slicing through tubers with a shovel. Loosen the dirt in a wide berth around the crown of the plant providing room around the roots so you don’t damage your crop. You may want to carefully lift the plant and use your hands to dig up the tubers, as they bruise easily. After digging up the tubers, shake off any excess dirt, but do not wash the roots.
The leaves are best in the early and mid-season but may be picked all summer long until the frost gets them in the late fall. Do not harvest too much, however, or you will be doing so at the expense of good tubers.
PROCESSING/CURING
Sweet potatoes need to be cured to develop maximum sweetness. Essentially this thickens the skin and heals over scratches that occurred during harvest. To begin that process a neighbor friend of mine recommends leaving the sweet potatoes out on the porch for the night after harvesting in cool weather, dirt and all. She said that’s what made them the sweetest!
Initially, they should be kept in a warm place but not too hot- about 75-85°F, ideally with a humidity of about 80-90% for 1-3 weeks. Warmer than that and they will sprout; too moist and they will spoil; drier than that and the skin won’t toughen up enough. Do not wash them however, as any residual moisture on the roots can cause them to spoil faster. Maintain good air circulation to prevent spoilage during curing. Placed in paper bags on the back porch in the shade with a wet towel on them works, placed one layer in a plastic grocery bag with holes on a sunny windowsill works, or in a storage tub on a rack with some water in the bottom works. Whatever your method, you have options. In the warm south where fall is still very warm (like here in Arizona) a garage or a shady garden shed works well for the location to cure them.
If you live in a more humid part of the United States an outdoor location in the shade works because the latter part of the summer usually includes humid weather. Some people pack them in crates of clean damp sand, but it is better if they have air circulation and are not touching. For this reason, you may opt to leave them in a single layer and use a small fan to improve the air circulation to prevent spoilage.
STORING
After curing, sort sweet potatoes and discard those that are bruised, sprouting or molding. You can then place them in the sand or wrap the tubers in a breathable newspaper and pack them in a box or basket for long term storage in a root cellar, basement, pantry, or garage. The ideal location for long-term storage would maintain a temperature range of 55°-60°F and 60% humidity for a minimum of 6 weeks. Storing in this way will improve the keeping quality and flavor yet more. If the storage location falls below 55 degrees for too long the centers of the potatoes may develop hard, white spots, but If it remains too warm, 60 degrees or higher, the potatoes may soften and shrivel and start to sprout. Stored properly, the tubers should last for up to 6 months.
Some people recommend putting an apple in each box of sweet potato tubers to prevent them from sprouting. This is probably because an apple releases ethylene gas as it continues to age. The gas acts as a growth suppression and fruiting hormone. Personally, I think that I would rather not find a rotten apple in my sweet potatoes a few months down the road, especially since The ripening enzymes found in the sweet potatoes themselves can accelerate the ripening process of other fruits and vegetables.
Without going through the effort for long-term storage you can keep sweet potatoes in a cool room for a few weeks in root form and a little longer in the fridge. For long-term cold storage (up to a year) they really should be diced or sliced, then cooked, or cooked then mashed before vacuum sealing and freezing. Adding some lemon juice to them will help maintain the vibrant color. We have found that slicing, roasting and freezing them works great for long term storage and convenient for later use.
The leaves work well frozen if you plan to use them within six months. For safety reasons we recommend blanching the leaves and then straining quickly and dropping them in ice water, then pat dry prior to freezing or dehydrating them. For leaves taken from our own yard we usually just rinse them and throw them in a freezer bag or use them directly.
USE IT:
TUBER VERSATILITY
Sweet potatoes can be used in curries, chutneys, casseroles, desserts, roasted, sauteed, boiled, baked, or cooked in a crockpot with other vegetables. They often make a superior substitute to pumpkin in dishes as well. Their uses are nearly endless. The drier, starchier varieties are sometimes used as a potato substitute, while the moist varieties don’t make good potato substitutes, but rather lend their own unique virtues to the culinary experience.
One of the best traditional uses is of course baked. The tubers should be washed clean, poked with a fork several times, then coated in olive oil and placed on a cookie sheet. Bake at 400°F for 40-60 minutes. Do not wrap in foil so that the sugars can caramelize. When they are done they will be soft when you squeeze them. Watch out it’s hot! Or you can cook them in the microwave on high for 4-6 minutes. They will be soft once cooled.
EAT YOUR GREENS!
Aside from the sweetest and tender root that is so familiar on our Thanksgiving plate, the leaves have a variety of uses in the kitchen as well. The leaves are great for stir fries, green smoothies, salads, and casseroles. One amazing quality is that the leaves hold flavor better than any green I have come across. If you season them well and saute in the flavor, they can be put into any dish such as quinoa or rice as a savory spinach substitute. One of our favorite recipes using the leaves is Savory Garlic Chicken Bake on a thick bed of sweet potato greens. While they do not disintegrate when cooking like spinach does, they cook down a lot and it is easy to use a whole bag full in one dish.
‘Japanese Red’ sweet potato vine
FEEL IT:
THE TUBERS
These naturally fat-free vegetables are rich in protein, fiber, sugars, and carbohydrates, but are lower in calories, and have a lower glycemic load than traditional Irish potatoes. The vegetable as a whole has a strong anti-inflammatory effect, whereas yams and Irish potatoes are moderately inflammatory.
An average sized cooked tuber without salt contains 37% of the recommended daily value of Vitamin C, along with Vitamin K, and B Vitamins Thiamine (B1), Riboflavin (B2), Niacin (B3), Pyridoxine (B6), and Folate (B9). This dish also provides 438% of the recommended daily value of Vitamin A, which comes in the form of carotene. Carotene, once quickly converted into Vitamin A, has powerful free-radical fighting properties. Additionally, it is rich in other antioxidants, anthocyanins, chlorogenic acid, coumarins, and other nutrients.
Let’s not forget the minerals! It contains approximately 28% of the recommended daily value of Manganese, as well as high concentrations of absorbable Calcium, Iron, Potassium, Phosphorous, Magnesium, and Copper.
THE LEAVES
We love our summer greens! Part of our beloved morning routine includes going out in the morning to forage greens from our landscape, including sweet potato leaves, for our morning green smoothie. This tradition is largely to take daily advantage of the nutritional supplement provided by the greens that we are using.
Sweet potato leaves have many of the same nutrients as the tubers and are a great source of vegetable protein, Calcium, and Iron, and are highly anti-inflammatory. They are a very good source of Vitamin A, Vitamin C, Vitamin E, Vitamin K, and B Vitamins Thiamine (B1), Riboflavin (B2), Niacin (B3), Pyridoxine (B6), and Folate (B9). As a green leafy vegetable, they are also high in Magnesium, Phosphorus, Potassium, and Manganese. Vitamins A, E, D, and K are fat-soluble minerals essential for building strong bones, cartilage, teeth, and hair.
Sweet potato leaves contain a small amount of oxalic acid, which adds to the pleasant flavor, but not enough to harm and therefore may be used raw as well as cooked. The leaves are also a great source of dietary fiber and very beneficial for maintaining the digestive tract, as evidenced by the slightly mucilaginous texture. There is also strong evidence that many nutrients in the leaves are anti-mutagenic, therefore showing potential as a wholesome anti-cancer food.
FINAL THOUGHTS
The sweet potato plant is one of the best options for a great edible landscape, not to mention one of the easiest groundcovers to grow! We hope this information leads you to a bounteous harvest in your progress to paradise!
How are your sweet potatoes growing? Any ideas, suggestions, or recipes that have worked for you? Please comment to share!
Human beings cannot fully comprehend the microbial interactions going on beneath our feet, in the soil, and at the rhizosphere, or root-zone of our plants. Generations of thousands of species of living microbial populations explode with complex economies of extraction, manufacture, construction, trade, and war, and many individuals go extinct within days or weeks. For some, their entire lives are mere minutes.
But It all starts at ground zero- the surface. Surface or subsurface dwelling detritivores such as worms, earwigs, crickets, wood lice, termites, and springtails chew up debris and excrete the remains as frass, a delectable food source for many other fungi and bacteria. These organisms churn some of this debris down into the root zones of plants, where it is further processed by soil microorganisms.
Soil microorganisms, or microbes, include hundreds of thousands of species of bacteria, archaia, fungi, protozoa, nematodes, and others all interacting in a community network of billions of different interactions- feeding, and feeding off of, each other and working in a dynamic group. Sometimes they are symbiotic, sometimes not.
These organisms are creating and processing an innumerable array of chemicals, many of which are only useful to a small handful of other organisms with whom they form relationships. Some microbe species are called saprophytes. These may or may not form direct associations with the plants and do not need to live in or on them for survival.
Many of these organisms are efficient nutrient extractors and foes of pathogenic fungi. They can be highly beneficial in their extraction abilities and in their abilities to parasitize plant pathogens, but many may also compete with, or consume other beneficial microbes. An example of this is Trichoderma viride. Several species of Trichoderma are often used as a readily available fast acting filler ingredient in microbial mixes, but will opportunistically feed on both pathogenic fungi, as well as many species of beneficial mycorrhizal fungi, making them particularly dangerous to a system where mycorrhizal fungi is wanted, and under certain conditions, may even parasitize the plant itself, or humans with compromised immunity.
Some organisms extract phosphorus and potassium ions from the mineral layers deep below the plant using chemicals such as carbonic, oxalic, citric, and acetic acids. Expansion and contraction of soils allow access to trapped potassium. Others are extracting phosphorus from minerals, abandoned roots, and the bodies of other organisms.
Still other bacterias and fungi are bounty hunters- seeking highly toxic chemicals to capture, and break down into new resources, and then trade those resources to others. Extremophiles are organisms that can live in extreme environments, such as highly toxified soil, or extremely high or low temperatures. Many scientific studies have been conducted in which plants have been grown with rich colonies of specific microbes in soil that was highly contaminated with various contaminants. When the plants were harvested they were analyzed for toxins, and no residual toxins were found in the harvested plant- all thanks to the healthy populations of microbes in the soil.
All these interactions are made possible by photosynthesis of sunlight and gases, and the resulting production of sugars. Every microbe has a different function and each consort will grow and thrive depending on what their environment has to offer.
What is Mycorrhizal Fungi?
Plants extract minerals from the soil using secretions of carbonic, oxalic, citric, and acetic acids and other enzymes in root exudates, but fungi are more efficient. Plants, on the other hand, are extremely efficient at turning sunlight into sugars through the process of photosynthesis. By forming a mutually beneficial relationship of exchange the plants can barter sugars for nutrients from the fungi, thereby each organism performing the tasks that they are particularly suited for and getting the rest of what they need from the other. Many species of fungi have specific mutually beneficial relationships with certain species of plants. These organisms may be completely dependent on the roots of plants, often attaching themselves, thereby shortening the distance and increasing efficiency of the exchange.
For example ericoid mycorrhiza have a relationship with blueberries and related plants. The plant’s relationships with these organisms will improve your blueberry crop and plant hardiness. Orchids form a relationship with another group of mycorrhizal fungi.
One of the most important groups of beneficial fungi is the ectomycorrhizal fungi group, which forms relationships with many hardwood and conifer tree species, more than 5% of all plants tested for these relationships. This group of fungi weave sheaths of mycelial lattice around the individual roots like an impenetrable hedge, or filter, thereby protecting the root from the entrance of pathogenic bacteria and other organisms, toxic metals, and other harmful chemicals. In an effect, this lattice of mycelium becomes the gatekeeper. In short, if the population of ectomycorrhizal fungi is healthy, the plant may be completely resistant to soil-borne disease.
By far the most useful clade of mycorrhizal fungi for gardeners and orchardists is one which forms a strong beneficial relationship with more than 85% of all plants that have been tested for mycorrhizal relationships. This is known as the endomycorrhizal fungi group. In this group, the allied populations of fungi embed mycelial hyphae, or fungal “roots,” into the roots of the plant and can then serve as a sort of root extension, extracting nutrients that are otherwise unavailable to the plant and making an exchange. This can greatly accelerate the growth of the plant’s roots, and thereby, its overall health.
These “root extensions” can embed themselves into the root systems of many plants and species simultaneously. Thus the root exudates of one plant may actually become the resources of another through the mycelial network, and visa versa. Because of how these organisms interact with the root system of the plant, they are mutually exclusive. If they have a relationship with ectomycorrhizal fungi they won’t have a relationship with endomycorrhizal fungi.
Allied populations of endomycorrhizal fungi embed themselves into the cellular structure of plants, sending mycelial hyphae into the soil to extract nutrients to trade with the plant for some of its offered sugars. Many are hungry for carbon and a few spend their energy sequestering carbon by manufacturing it into a sort of soil glue called glomulin. This very stable organic carbon glue makes up a huge amount of soil carbon by volume in healthy soils.
Fungi has a different type of respiration system than plants. Plants inhale carbon dioxide and exhale oxygen. The Animal and Fungi kingdoms breathe in oxygen and exhale carbon dioxide. It’s opposite of the actively growing specimens in the plant kingdom. Thus another way that a close relationship with fungi is beneficial to the plant is via the elevated CO2 levels in the rhizosphere where fungi is present. CO2 is inhaled through the root system as well as the leaves, and both the plant and the fungi benefit.
The Rhizophagy Cycle
The term Rhizophagy Cycle represents the process by which the plants attract several specific species of bacteria by secreting superoxides into the soil from their root tips. The attracted bacterias are then taken in by the plant, as if sucked up by a straw, and cycled throughout the entire system of stems, leaves, flowers, and fruits (and yes, become a nourishing part of our foods and digestive flora).
As the bacterial cells travel through the plant active enzymes in the plant’s fluid dissolve the bacterial cell wall. The cell wall is broken down into amino acid sugars (a very usable form of nitrogen) and assimilated by the plant as a nitrogen source needed for growth. As the bacteria near the end of their journey through the plant they are then excreted back out into the soil as protoplasts, or cells without a wall. The bacteria then regrows its cell wall, is attracted back to the plant by its superoxide secretions and the cycle begins again.
The Nutrients
Misunderstanding N-P-K
Many of the scientists and farmers who study the rhizophagy cycle have determined that nitrogen is rarely a limiting nutrient factor when the soil microbiome is healthy. Most of the time, plants are able, through their relationships with fungi, bacteria, archaia, and other organisms, to supply all the nitrogen needed for necessary growth, environmental factors contingent.
However, our misconceptions of nitrogen (N), phosphorous (P), potassium (K) and other nutrients have resulted in a dramatic change in soil dynamics. In human ignorance we think that if we give the plant some N-P-K it’s all going to be fine. As a society we have an expectation that we must feed our plants with chemicals, and that we can somehow substitute the interdependent relationships embedded in evolutionary plant DNA with human contrived solutions. In reality, these common misconceptions come from not understanding things that we cannot see.
In fact it has been proven time and again in university studies (some on plots in continuous plantings for more than a hundred years) that a continual dosage of nitrogen fertilizer over time will decrease carbon. Carbon = fertility, therefore, decreased carbon means decreased fertility. Fertility implies many things, including the soil’s ability to retain an adherent structure. Without this, the result is rapid desertification.
Microbes use approximately 24:1 to 35:1 Carbon to Nitrogen ratio optimally to break down material. Different sources of organic material supply different ratios, and regardless of the ratio, as long as moisture is consistent, you’ll eventually get compost,… eventually. If microbes have a lot of cellulose carbon available, they must have nitrogen to break it down, even if it means taking it from the plant or from available soil N.
Why would it be any different with nitrogen? It’s not. If microbes have nitrogen, they must have carbon, which means that they will consume all the necessary carbon from the soil carbon bank in order to process the available nitrogen, thereby resulting in decreased fertility.
So farmers and scientists have traditionally been applying way more nitrogen than the plants actually need and the soil microbes feel it their eternal duty to create a balance. Thus, poof! Your carbon just vaporized into carbon dioxide gas. Along with your optimum fertility. Better to be high on the stable carbon side, thereby culturing an environment that encourages a healthy population of bacteria that can supply that nitrogen in forms that nature’s complex system is used to doing. But burning up available carbon may not be the only down side of heavy applications of ionized nitrogen; it may cause other challenges as well.
Endophytes, which are any beneficial bacteria that live in or on plant material, such as on and inside seeds, are generally quite robust. They usually have little problem surviving treatments such as scalding water baths, high chlorine concentrations in municipal water supplies, and other factors, but are actually quite sensitive to ionized nitrogen. The epitome of this irony? Fertilizer coated seeds. Recent scientific evidence has shown that many attempts to improve germination and active growth of seedlings by applying a coating of fertilizer to crop seed, has resulted in comparatively poor initial growth compared to untreated seed. As healthy populations of endophytes are an important addition to the successful growth of new seedlings, this is likely the reason.
Unfortunately few available lab tests for available nitrogen will account for the nitrogen derived from the amino acid sugars provided by the breakdown of bacterial cell walls within the plant itself, or in the surrounding soil profile and generally only account for available ionized nitrogen.
No One Fertilizes the Forest
If you spend any amount of time in wilderness areas, you may find wild fruit trees and berry bushes in the forest for which nobody is broadcasting fertilizer, and yet they’re loaded with fruit. Why is that? You may see trees that are growing out of a crack of rock on the side of a cliff. There’s not even any soil there! Where are they getting NPK from? Certainly not from agricultural fertilizer or runoff.
They are getting it from bacteria on their roots. No human is going up there and pouring a watering can of Super-gro fertilizer down the crack of the rock on the side of the cliff. If they did they would probably kill that tree. This plant is actually farming bacteria on its roots- feeding off of the nutrients from the bacteria. Those bacteria are breaking down rock and extracting minerals the tree needs through root acid exudates and enzymes. Nutrients are supplied to the plant in exchange for the one thing that the plant has in relative abundance: sugars from sunlight.
At Eden Institute, we propose that if you have a healthy population of microbes you may not need to fertilize at all. A bold proposition to be sure, but nature does the job that it was designed to do. And once that population is established people don’t need to be there to do it. Many, many plants are very beautiful and productive with little to no human intervention.
If farmers, gardeners, and landscapers were to give up fertilizer and instead focus on introducing and sustaining the beneficial microbes, over time these microbes will adapt with interactive populations that have the ability to give the plant everything that it needs, including nitrogen, phosphorus, and potassium, the “essential” N-P-K.
Soil Nutrition = Food Nutrition
The United States Department of Agriculture (USDA) recently published a comparison of 13 different nutrients in 43 different garden crops from 1950 to 1999. The results were quite telling. The experiment first adjusted data to account for differences in moisture content before calculating ratios of nutrients in foods. While there was no statistically reliable decline for 7 of the 13 nutrients tested, there was a statistically significant reduction for 6 primary nutrients: protein, calcium, potassium, iron, riboflavin (vitamin B2) , and ascorbic acid (vitamin C). The nutrient density of our modern average grocery store produce pales in comparison from that produced in 1950.
In addition to the actual mineral and nutrient content of our modern produce, the “living” probiotic quality of our foods is empty by comparison because of modern agricultural practices. Beneficial bacteria are normally taken in at the roots and translocated throughout the plant; they’re not just found in the roots, but also in the leaves, tissues, flowers, fruits, and seeds. The fruits and vegetables grown in soil with a healthy microbiome will themselves have a healthy dose of those same probiotics resulting in sweeter flavor, more easily digestible, mineral rich, nutritionally dense, and medicinally capable. As an aside, studies have even been performed showing that foods that are grown in a healthy microbiome may also last longer on the grocery shelf and in the refrigerator.
Those same microbes will add to, and diversify, your gut flora making nutrients more readily available to your body. A healthy gut flora also leads to an internal production of B Vitamins, from the breakdown, and subsequent digestion of gut bacteria. You may be getting as much B Vitamins from these microbes as you do from the food that you eat. The bacteria is feeding your body in a similar way that it feeds the plants. Those microbes end up populating our digestive systems resulting in a diverse gut flora that displaces pathogenic gut bacteria and is essential for good health. Without this plant/bacteria relationship and cycle our food will be devoid of the very bacteria that our digestive system needs to thrive.
Living Soil Amendments
Compost
Compost can be fantastic… if done right. It can potentially be a microbially diverse, nutrient rich soil amendment that can change the productivity of your agricultural ventures. But it can also contain pathogens. It’s soil life consists mostly of saprophytes which are bacterias and fungi that can be powerful for breaking down nutrients, but they may, or may not, have a direct relationship with plants.
Manures
Manures may contain the primary bacteria organisms essential to the healthy production of healthy plants, but may also contain high concentrations of salts, undigested weed seeds, and if the livestock was raised in densely populated confined stockyards and feedlots, may contain hormones, chemicals, and pathogenic species that are highly detrimental to human health. They also do not include the mycorrhizal fungi essential for optimum plant growth.
Traditional Microbe Products
Traditional microbial soil amendment products can be a very useful option to populate species of beneficial microbes in your soil microbiome. But they also have some downsides.
Traditional microbial soil amendment products are usually liquid in form because they work faster as a liquid, but either need to be refrigerated or they have a short shelf-life. Dry concentrated microbe products contain microbes that are stunned through a freeze-drying process that detrimentally affects their productivity for an extended timeframe and usually take weeks to populate after reconstitution. They often contain cheap, easy to obtain filler organisms that work quickly to break down material into available nutrients, but are usually pathogenic to beneficial mycorrhizal fungi. And of course they are designed as a mixture of a limited number of microbes added together much like a recipe that you could compile yourself from online wholesale sources.
Soil Fertility Accelerator
Soil Fertility Accelerator (SFA) is a step above the rest. This product contains no fillers, is pathogen free, is not a blended recipe, but rather a naturally developed consortium of hundreds of millions of microorganisms that are in “suspended animation” and will activate within seconds upon reconstitution with water.
SFA also contains the most powerful biostimulants and microbial food sources available, necessary for the support of native beneficial microbial populations. It increases Brix levels, plant proteins, soil carbon, soil fertility, plant health, vigor, and nutritional content of fruits and vegetables.
Conclusion
Understanding, and taking advantage of the powerful interactions that are taking place below our feet is the first step to healing our soils. We now have what is necessary to make that happen.
