Fruit Facts from
the
California Rare Fruit Growers, Inc.
Mulberry
Morus spp.
Moraceae
Common
Names: Mulberry
Species: Mulberry (Morus
alba L.), Black Mulberry (M. nigra L.),
American Mulberry, Red Mulberry (M.
rubra L.). Hybrid forms exist between Morus alba and M. rubra
Related
Species: Korean Mulberry (Morus australis),
Himalayan Mulberry (M.
laevigata).
Distant
Affinity:
Breadfruit (Artocarpus
altilis), Jackfruit (A.
heterophyllus), Fig
(Ficus
spp.), Che (Cudrania
tricuspidata), African Breadfruit (Treculia
african).
Origin:
The
white mulberry is native to eastern and central China. It became
naturalized in Europe centuries ago. The tree was introduced into
America for silkworm culture in early colonial times and naturalized
and hybridized with the native red mulberry. The red or American
mulberry is native to eastern United States from Massachusetts to
Kansas and down to the Gulf coast. The black mulberry is native to
western Asia and has been grown for its fruits in Europe since before
Roman times.
Adaptation:
The white mulberry, and to a lesser extent the red mulberry, are quite
tolerant of drought, pollution and poor soil. The white mulberry is
considered a weed tree in many parts of the country including urban
areas. The black mulberry is more fastidious, faring less well in cold
climates or areas with humid summers. The white mulberry is the most
cold-hardy of the three species, although this varies from one clone to
another. Some are damaged at 25° F, while others are unfazed at
-25° F. Red mulberries are hardy to sub-zero temperatures. The
black mulberry is the least cold-hardy of the three, although again
cold tolerance seems to depend on the clone. In general it is limited
to USDA Hardiness Zone 7 (0° to 10° F average minimum) or
warmer. They have been planted only to a limited extent in America,
mostly on the Pacific Coast. The mulberry makes a good town tree which
will grow well in a tub.
Description
Growth Habit:
All
three mulberry species are deciduous trees of varying sizes. White
mulberries can grow to 80 ft. and are the most variable in form,
including drooping and pyramidal shapes. In the South on rich soils the
red mulberry can reach 70 ft. in height. The black mulberry is the
smallest of the three, sometimes growing to 30 ft. in height, but it
tends to be a bush if not trained when it is young. The species vary
greatly in longevity. Red mulberry trees rarely live more than 75
years, while black mulberries have been known to bear fruit for
hundreds of years. The mulberry makes an attractive tree which will
bear fruit while still small and young.
Foliage:
The white mulberry is so-named for the color of its buds, rather than
the color of its fruit. The thin, glossy, light green leaves are
variously lobed even on the same plant. Some are unlobed while others
are glove-shaped. Leaves of the red mulberry are larger and thicker,
blunt toothed and often lobed. They are rough on their upper surfaces
and pubescent underneath. The smaller black mulberry leaves are similar
to those of the red mulberry, but with sturdier twigs and fatter buds.
The species vary in the time of year they begin to leaf-out. White
mulberries generally come out in early spring, almost two months before
black mulberries.
Flowers:
Mulberry trees are either dioecious or monoecious, and sometimes will
change from one sex to another. The flowers are held on short, green,
pendulous, nondescript catkins that appear in the axils of the current
season's growth and on spurs on older wood. They are wind pollinated
and some cultivars will set fruit without any pollination.
Cross-pollination is not necessary. In California mulberries set fruit
without pollination.
Fruit:
Botanically the fruit is not a berry but a collective fruit, in
appearance like a swollen loganberry. When the flowers are pollinated,
they and their fleshy bases begin to swell. Ultimately they become
completely altered in texture and color, becoming succulent, fat and
full of juice. In appearance, each tiny swollen flower roughly
resembles the individual drupe of a blackberry. The color of the fruit
does not identify the mulberry species. White mulberries, for example,
can produce white, lavender or black fruit. White mulberry fruits are
generally very sweet but often lacking in needed tartness. Red mulberry
fruits are usually deep red, almost black, and in the best clones have
a flavor that almost equals that of the black mulberry. Black mulberry
fruits are large and juicy, with a good balance of sweetness and
tartness that makes them the best flavored species of mulberry. The
refreshing tart taste is in some ways reminiscent of grapefruit.
Mulberries ripen over an extended period of time unlike many other
fruits which seem to come all at once.
Culture
Location:
Mulberries need full sun and also adequate space. The distance between
trees should be at least 15 ft. The trees should not be planted near a
sidewalk. The fallen fruit will not only stain the walkway, but are
likely to be tracked indoors. The trees are quite wind-resistant with
some cultivars used as windbreaks in the Great Plains region.
Soil:
Mulberries like a warm, well-drained soil, preferably a deep loam.
Shallow soils such as those frequently found on chalk or gravel are not
recommended.
Irrigation:
Although somewhat drought-resistant, mulberries need to be watered in
dry seasons. If the roots become too dry during drought, the fruit is
likely to drop before it has fully ripened.
Fertilization:
Mulberries generally thrive with minimal fertilization. An annual
application of a balanced fertilizer such as 10:10:10 NPK will maintain
satisfactory growth. In California mulberries usually need only
nitrogen.
Pruning:
No
special pruning techniques are needed after the branches have been
trained to a sturdy framework, except to remove dead or overcrowded
wood. A mulberry tree can be kept to a tidy form by developing a set of
main branches, and then pruning laterals to 6 leaves in July in order
to develop spurs near the main branches. It is not advisable to prune
the trees heavily since the plant is inclined to bleed at the cuts.
Cuts of more than two inches in diameter generally do not heal and
should be avoided at all cost. The bleeding will be less severe if the
tree is pruned while it is dormant.
Propagation:
Mulberries can be grown from seed, although the plants can take 10
years or more to bear. Seed should be sown as soon as extracted from
the fruit, although white mulberry seeds germinate better after
stratifying one to three months before planting.
Sprig budding
is the most common method for grafting mulberries. A T-cut is made in
the rootstock and a smooth, sloping cut is made on the lower end of the
scion. The scion is then inserted into the T and wrapped and sealed.
Other types of grafts are also usually successful, although there may
be incompatibility between white and black mulberries. Hardwood,
softwood and root cuttings also are suitable methods for propagating
mulberries. Softwood cuttings of white mulberries root easily when
taken in midsummer and treated with rooting hormone. Red mulberries are
less easily rooted. Black mulberries are also somewhat difficult to
propagate since they tend to bleed a lot.
Pests and
Diseases:
Mulberries are generally free of pests and diseases, although cankers
and dieback can occur. In some areas "popcorn disease" is an occasional
problem, in which fruits swell to resemble popped corn. M. alba/M.
rubra hybrids are particularly prone to this condition.
The disease
carries on from one season to the next, so collecting and burning
infected fruits help control it. The ripe fruit is very attractive to
birds, but there is usually enough fruit left over for harvesting.
Harvest:
White and red mulberry fruits (and hybrid fruits) are ready for harvest
in late spring. The fruit of black mulberries ripen in summer to late
summer. The fruits of white mulberries are often harvested by spreading
a sheet on the ground and shaking the limbs. A surprising quantity can
be gathered from a comparatively small and young tree. Black mulberry
fruits are more difficult to pick. As the berries are squeezed to pull
them loose, they tend to collapse, staining the hands (and clothing)
with blood red juice. Unwashed the berries will keep several days in a
refrigerator in a covered container. The ripe fruits of the black
mulberry contain about 9% sugar with malic and citric acid. The berries
can be eaten out of hand or used in any way that other berries are
used, such as in pies, tarts, puddings or sweetened and pureed as a
sauce. Slightly unripe fruits are best for making pies and tarts.
Mulberries blend well with other fruits, especially pears and apples.
They can also be made into wine and make an excellent dried fruit,
especially the black varieties.
Cultivars
Black Persian
M.
nigra.
Large black fruit, over an inch long and almost as wide. Juicy with a
rich, subacid flavor. The tree is fairly drought-resistant once
established.
Collier
M.
alba X M.
rubra.
Medium-sized, purplish-black fruit, 1-1/8 inches long and 3/8 inch in
diameter. Flavor sweet, with just a trace of tartness. Quality very
good, on par with Illinois Everbearing. Ripens over a long period. Tree
of medium size, spreading, relatively hardy, very productive.
Downing
The original Downing was a M.
alba var. multicaulis
plant grown
fromseed sown about 1846. The fruit was black with excellent flavor and
ripened from June to September. Other varieties have subsequently been
sold under the same name.
Illinois Everbearing
M. alba X M.
rubra.
Originated in White County, Illinois. Introduced in 1958. Black, nearly
seedless fruit large and very long, averaging 12 per ounce. Flavor good
to very good, very sweet, considered best by by many. Matures over
along season. Tree vigorous and somewhat dwarfed, extremely hardy and
productive.
Kaester
M. nigra.
Originated in Los Angeles. Introduced in 1971 by Nelson Westree. Large
black or deep purple, elongated fruit, 1-1/2 inches long and 1/2 inch
in diameter. Flavor very sweet, with good sweet/tart balance. Tree
bears heavily.
Pakistan
Originated in Islamabad, Pakistan. Extremely large ruby-red fruit 2-1/2
to 3-1/2 inches long and 3/8 inch in diameter. Flesh firmer than most
other named cultivars. Sweet with a fine balance of flavors. Quality
excellent. Tree spreading with large heart-shaped leaves. Recommended
for the deep South and mild winter areas such as southern California,
but usually performs satisfactorily in cooler areas.
Riviera
Originated in Vista, Calif. Elongated, deep purple-black fruits, 1 to
1-1/2 inches in length, 1/2 inch in diameter. Flesh slightly juicy and
very sweet. Very good dessert quality. Ripens over a long period, from
April to June.
Russian
(Tatarica)
Introduced into Europe from China about 1,500 years ago. Fruit
reddish-black, of good quality when completely ripe. Tree bushy, to 35
ft. tall, very hardy and drought resistant. Planted widely for
windbreaks and wildlife food.
Shangri-La
Originated in Naples, Fla. Large, black fruit. Good mulberry for the
Deep South and other areas. Hardy in U.S.D.A. Zones 7-9. Tree has very
large, heart-shaped leaves.
Tehama
(Giant White)
Originated in Tehama County, Calif. Very large, white-colored, plump
fruit, 2-3/4 inches in length and 1/2 inch wide. Very sweet, succulent,
melting flesh. Attractive, large-leaved tree. Probably best adapted to
mild winter areas.
Wellington
Originated in Geneva, N.Y. Reddish-black medium-sized fruit, 1-1/4
inches long, 3/8 inch in diameter. Form long, slender and cylindrical.
Flesh soft, of good flavor. Ripens over a period of several weeks. Tree
is heavy producer. May be the old cultivar New American, which was also
sold many years ago as Downing.
Further
Reading
Everett, T. H., ed. New Illustrated Encyclopedia of Gardening. vol. 7.
Greystone Press, 1960. p. 1190.
Facciola, Stephen. Cornucopia: a Source Book of Edible Plants. Kampong
Publications, 1990. pp. 391-392.
Johns, Leslie and Violet Stevenson, Fruit for the Home and Garden.
Angus and Robertson, 1985. pp. 173-176
Reich, Lee. Uncommon Fruits Worthy of Attention. Addison-Wesley, 1991.
pp 173-183.
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© Copyright 1996-2001, California Rare Fruit Growers, Inc.
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