THE ULTIMATE GUIDE TO GROWING AND USING MULBERRIES
MULBERRIES: BERRIES THAT RAIN FROM TREES
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
References:
https://www.growingmulberry.org/
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