Growing Mulberry: Morus species (2024)

Botanical Overview

The Mulberry family (Moraceae), includes Jackfruit, Figs, Mandarin Melon Berry, and Morus, the Mulberry genus, with 17 accepted species. Many mulberry hybrids exist, and identification can be difficult.
The name of the species does not indicate the color of the fruit, but rather the color of the leaf buds. For example, nearly all White Mulberry cultivars have black or purple berries.

Description

Form: Tree. Some dwarf cultivars grow as a shrub.

Lifespan: 500 to 1000 years for Morus nigra: Black Mulberry; 100-250 years for Morus alba: White Mulberry; 100-250 years for Morus macroura: Pakistan / Himalayan Mulberry; and 75 years for Morus rubra: Red Mulberry.

Leaf retention: Deciduous. Mulberries leaf out between winter and spring based on temperature, not length of day. The number of days temperatures must stay warm to induce leaf out varies by species and cultivar. White mulberries tend to leaf out later than Black and Pakistan mulberries by as much as one month.

Growth rate: Rapid for most species, but temperature dependent. Morus nigra has a slow growth rate.

Mature Size: 10-50' (3-15m) high and 10-30' (3-9m) wide, depending on cultivar.

Flowers: Male and female catkins (single-sex flower spikes) appear on separate trees. Male trees produce excessive amounts of allergy-causing pollen. Some female trees, however, such as those listed below, produce fruit automatically without male trees or pollen being present. In general, most female trees sold in nurseries do not produce male flowers.

Bloom: Spring, or spring and fall, or sporadically throughout the warm season, depending on cultivar.

Self-fruitful: Most cultivars sold at nurseries are female-only and set seedless fruit without pollination. A few cultivars require a second tree as a pollenizer. Those produce seedy fruit or none at all if not pollinated.

Years before fruiting: 2-3 from rooted cuttings or if grafted onto rootstock, 8-10 if grown from seed. Morus nigra, Black Mulberry, often takes up to 15 years to attain full production.

Fruit: The "berry" is an aggregate fruit, with many small round fruits clustered together. Dropped fruit will stain sidewalks and carpets, although some cultivars are stainless. A berry's flavor depends on its ripeness, the cultivar, soil moisture, and sunlight. Morus nigra (Black Mulberry) fruit are considered to be the best tasting of all mulberry species.

Months for fruit to ripen: 2-3. Berries ripen a few at a time on most cultivars. Berries will continue to ripen to black if picked when red. For several cultivars, including Black Mulberry, the fruit is fully ripe on the tree when it changes from shiny black to dull black.
Morus alba and Morus macroura fruit can be harvested by shaking the branches and letting the fruit fall onto a tarp on the ground. Morus nigra fruit do not release from the stem until second or third day ripe, when they fall to the ground, so scissors or clippers are needed to harvest all of them. However, fully ripe berries will often come off in the hand with a slight pull, making clippers unnecessary if harvesting is done every day. In strong winds, Morus nigra trees keep their ripe fruit a day or two longer while that of other mulberry species blow off when they are nearly ripe.

Storage after harvest: Unwashed berries will keep two days in a refrigerated, closed container. Freezing, eating the same day, or baking immediately is recommended. They can also be dried. Fresh mulberry fruit is too perishable to ship and is not carried in stores.

Leaves: Green, serrated edges, variable in shape, turning yellow in fall. The date of leaf-out in late winter or spring varies by cultivar.
Morus nigra leaves, underneath, are uniformly covered in soft hairs. Topside, they are covered in short, stiff hairs and are more resistant when stroked toward the stem rather than away from the stem. Morus alba leaves can be stroked topside in either direction with the same effort. The leaves of Morus alba also have a waxy, glossy appearance on top while the those of Morus nigra are relatively dull.

Stems: No thorns. The milky sap is a skin irritant.

Roots: Aggressive, extensive, lateral roots are no more than 2' (0.6m) deep, extending beyond the tree's drip line. Smaller, vertical sinker roots grow from the laterals. Keep these trees away from sidewalks, driveways, foundations and septic systems to avoid damage from roots.

Cultivars of Note:

Morus nigra, Black Mulberry, cannot hybridize with other mulberry species because it has 308, instead of 28, chromosomes in its genome. All hybrids are between other species.

Morus nigra 'Persian': Black Mulberry Self fruitful, strongly staining, black fruit to 1.25" (3cm), with an excellent sweet berry flavor. Its fully ripe berry tastes like the best flavor component of every good-tasting berry species known, combined into one berry. This tree slowly grows to 30' (9m) high, in USDA zones 5-11. Morus nigra handles higher alkaline soil better than other mulberries.

Morus nigra 'White Persian': White-fruited Black Mulberry A variation of 'Persian' Black Mulberry. Self fruitful, non-staining, white fruit to 1.25" (3cm).

Morus nigra: Dwarf Black Mulberry A self-fruitful dwarf cultivar, producing strongly staining black berries, varying in size 1/4-1/2" (0.6-1.25cm) long, with an excellent sweet berry flavor. It produces both a spring and a fall crop, gradually increasing production over many years. The small berries are a bird magnet, resulting in purple bird poop everywhere, but this can be reduced by covering the tree in bird netting and by timely harvesting. The tree grows 8-12' (2.4-3.7m) high. Fertilizing with organic fertilizer in the second and third years in winter will speed growth. USDA zones vary according to rootstock, either 5-11 or 7-11. Dwarf Black Mulberry trees do well in large containers. This tree is less suited for dry climates because its roots do not grow deep fast enough, needing water more often for years after regular sized trees have put down deeper roots and become more resistant to drought.

Morus hybrid: 'Shangri La' Mulberry Self fruitful, staining, black fruit with a popular, sweet-tart flavor, and 1.5" (3.8cm) long berries. It grows 25' (7m) high in USDA zones 6-10 and originated in Naples, Florida. It is prone to bloom early and lose fruit or even small branches when late frosts occur.

Morus alba: 'Dwarf Everbearing' Mulberry Self fruitful, strongly red-staining, small black berries; grows 8-12' (2.4-3.7m) high. USDA zones 5-11. This tree is often misrepresented as Morus nigra.

Morus alba: 'White Fruited' White MulberrySelf-fruitful, non-staining, white colored berries to 1" (2.5cm), with a sweet white-peach-and-honey flavor. These cultivars may grow 30' (9m) high.
'Sweet Lavender' is a pink to light purple-tinged variation.
Birds are less attracted to white fruit. White colored fruit of white mulberry trees make the best-tasting dried mulberries.

Morus macroura: Pakistan / Himalayan Mulberry
Self fruitful, non staining, less juicy, up to 4" (10cm) long, black to reddish-black fruit. The fruit flavor is an interesting combination of raspberry and purple grape, only slightly sweet, and dependent on soil and climate. The long fruit can be blown off young trees when unevenly ripe by strong winds. During the first two years after planting, the tree will have poor tasting fruit and suffer significant fruit drop because its roots will not be long enough to sustain production. By its third year in the ground, the fruit will have better flavor and more will remain on the tree until ripe. The tree will need deep watering as often as weekly when fruiting after leaf-out during its first five years. This tree grows 25-30' (7.6-9m) high. It is limited to USDA zones 8b-10 and its branches are hardy to 25°F (-4°C).

Morus macroura: 'White Pakistan' Non-staining, up to 4" (10cm) long, yellow-white fruits, less juicy, with a slightly sweet honey-like flavor. It grows in USDA zones 8b-10 and to 25-35' (7.6-10.7m) high. 'Australian Green' is a variation tasting like honeydew melon.

Morus alba or hybrid: 'Weeping Mulberry' / 'Pendula' Not self-fruitful, staining, reddish-black, poor-tasting fruit if pollinated. An ornamental that grows 8-15' (2.4-4.5m) high and wide.

Wildlife: The fruit attracts birds and squirrels. Bird netting draped over the tree can be used to protect fruit from birds. Bird droppings from most cultivars of mulberry will stain.

Toxic / Danger: The milky sap is a skin irritant. Unripe fruit will cause an upset stomach.

Cultivation and Uses

USDA hardiness zones: 5-11, depending on cultivar.

Chill hours: Under 200, possibly none, for cultivars listed on this page.

Heat tolerant: Yes, however, fruit production is highest between 75-85°F (24-29°C), drops substantially above 85°F (29°C), and stops at 90°F (32°C).

Drought tolerant: Yes.

Sun: Full sun.

Planting: Locate mulberry trees in full sun, in well-draining soil, 30' (9m) away from a house to avoid root damage to foundations. If the berries are staining, do not plant near walkways to avoid carpet stains from fallen fruit. Also plant 50' (15m) away from water pipes, sewer lines and septic systems as the roots can clog pipes quickly. The distance between trees should be at least 10' (3m). Dwarf cultivars can be grown in containers.

Soil: Mulberries need well drained soil, but are otherwise tolerant of soil types. Acidic to neutral soils are preferred, and alkaline soils may slow growth, but the trees will survive. Mulberries are moderately salt tolerant.

Fertilize: Organic fertilizer can be used once a year mid-winter but fertilizing is not usually necessary except for dwarf cultivars. Do not use organic fertilizer for at least two months after a tree is first planted.
Avoid high nitrogen fertilizers, such as ammonium sulphate, because that results in rapid, weak growth which is easily damaged by freezes and strong winds.
Mulberries are susceptible to iron, copper and boron deficiency in alkaline soil, although Morus nigra is somewhat less susceptible.

Water after becoming established: Deep water every one or two weeks starting with leaf break and throughout the warm season, accounting for rain. Reduce water to once a month at the start of November to encourage dormancy and while the tree is leafless. Mulberries should be deep watered consistently, as often as once a week, when fruiting. Fruit drop or dried fruit is a sign of insufficient water. Because most mulberries become very large, they will eventually need a lot of water unless trimmed to maintain a certain size. In a dry climate, dwarf varieties that produce large fruit may be preferable.

Mulch: Use organic mulch, inside the drip line and 8" (21cm) away from the trunk, to reduce evaporation loss and soil temperature. Wet mulch touching the trunk causes fungal diseases.

First Two Years' Care: In the first two years after planting, deep water as often as once a week, allowing for rain, to develop a strong root system.

Pruning and weeding: It is generally recommended not to prune in the first year so that the plant may attain sufficient root growth. Pruning in the winter when trees are dormant results in less sap flow, but the trees respond with strong spring growth. If dwarfing is desired, some recommend pruning in the middle of summer when the trees respond less vigorously to being pruned.
Another pruning technique to reduce tree height, during the first winter in the ground, is to cut the central trunk low, and allow new leaders (main vertical trunks with side branches) to grow. The next winter, all but two leaders are removed, and in the spring, one new leader is allowed to grow. Each following winter, the oldest leader is removed and one new one is allowed to grow, so there will always be three leaders, one year apart in age.
Mulberries do not need to be pruned unless they develop crossing branches in the middle. Prune off no more than 25% to avoid sending the tree into shock.
If you wish to keep a tree at a desired height, start pruning when the tree is young.
Mulberries bloom partly on spurs of old wood, but mostly on new wood, so pruning does not eliminate the entire crop. Pruning after the spring crop will result in the most fruit in the following year.
Remove all plants growing in the ground under the tree canopy to avoid competition for nutrients.

Litter: Fruit litter if not harvested, leaf drop late fall or winter.

Propagation: For Morus alba, take softwood cuttings in summer and plant in starter mix. For Morus nigra, take 1/2" (1.25cm) diameter hardwood cuttings in winter and plant in starter mix, in an enclosed container, to maintain high humidity. Morus nigra is more difficult to start from cuttings, however it will graft to other mulberry species.
Seeds do not usually breed true and will not produce the most desirable type of cultivar, the parthenocarpic (self-fruiting) female tree which produces seedless fruit.

Pests: Mulberry is prone to root rot in poorly draining soil. Root nematodes can also be a problem.

Uses: Edible fruit and leaves, ornamental, shade, bird garden (non-staining berries are preferred). Dark-colored mulberries can be used as a substitute berry in blackberry recipes and wine. Mulberries are frequently used to make sherbet, ice cream, jam, jelly, and pies. White colored mulberries pair well with apples and pears and can be used in most recipes needing a mild-flavored berry. Mulberry leaves are used in cooking like grape leaves, and also to make a tea.

Comments

The advantages of mulberry trees are:
[1] They are very easy to grow and tolerate difficult soils and climates.
[2] Modern female trees of all cultivars produce very delicious, seedless fruit at least once a year without pollination and without the presence of a male tree.
[3] Mulberries are good shade trees that drop their leaves in winter, allowing winter sun to warm a summer-shaded location.

The disadvantages of mulberry trees are:
[1] They have very aggressive roots and must be kept at least 50' (15m) away from water lines, sewage lines, and septic systems.
[2] Many cultivars have staining berries which can make a mess on walkways if not harvested and may result in widespread staining bird poop when birds eat the fruit. White fruited cultivars and Pakistan mulberries do not stain.
[3] The fruit perishes quickly and should be eaten, frozen, or cooked the day of harvest.
[4] The tree needs plenty of water in hot summers and cannot survive without supplemental water in very dry regions.

When a plant is labeled as "Non-fruiting Mulberry", it is a pollen producing male and should be avoided.

Some counties and cities erroneously ban all mulberry trees as pollen producers. However, self-fruiting, non-pollen-producing female trees are allowed in many.

Silkworms are fed the leaves of Morus alba or Morus macroura. They will not eat Morus nigra leaves. Morus alba was originally imported into North America for silkworm production. It has naturalized throughout most of the continent and hybridized with Morus rubra. Morus nigra has naturalized in only a few states.

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