The Kwai Muk, a Tropical
Fruit Tree for southern Florida
Scientific
name: Artocarpus
hypargyraeus, A. lingnanensis
Family: Moraceae
Abstract:
The kwai muk, a fruit tree native to Southern China, is little known in
Southern Florida although it has been grown here since 1927.
The
trees in Florida were introduced as Artocarpus hypargyraeus
Hance ex
Benth., but may be A.
lingnanensis Merr. This small, handsome tree has
a dense, rounded canopy and grows best in full sun. The small leaves
are dark green and leathery, and are retained on the tree throughout
the year. The tree grows well in the soils and climate of Southern
Florida.
Small trees are easily injured by frost,
but mature trees will survive brief exposure to temperatures of 25-26°F.
The
fruit is ovoid to globose, 1.5- 2 inches in diameter, with a yellow,
finely pubescent surface. The soft pulp is orange-red in color, with a
melting texture and a pleasant, subacid flavor. The fruit matures from
August to October. The fruit usually is eaten fresh, but also can be
preserved with salt, with sugar syrup or by drying. This tree should be
planted more extensively in gardens of Southern Florida because of its
attractive appearance and its useful, palatable fruit.
Several
species of the genus Artocarpus
are valued for their edible fruit in
the tropics. The breadfruit and the jackfruit are the best known of
these. Another, the kwai muk, has proved to be well-adapted for
cultivation in Southern Florida. The plant was first introduced to
Florida as Artocarpus
hypargyrae Hance (1); the name was later modified
to A. hypargyraeus
Hance ex Benth. (2). It now appears that the plants
here may be of a closely-related species, A. lingnanensis
Merr.(6, J.
Popenoe, Fairchild Tropical Garden personal communication).
The
kwai muk is from China, where its native range includes southern
Kwangtung Province, Hainan Island and Hong Kong. It has been introduced
to other areas of the tropics, primarily in botanical gardens and
experiment stations, but is not well known outside its native area.
The
kwai muk was first introduced to Florida in 1927 (1), but is still
little-known or planted here. The tree has attributes which recommend
it for cultivation in home gardens in the state. The purpose of this
paper is to describe the kwai muk and bring it to the attention of
growers of tropical fruit in Florida and elsewhere.
DESCRIPTION
The
kwai muk tree grows to a height of 15 ft in China (6); mature trees in
Florida generally attain a height of 20-25 ft. The following
description is based on observations of trees growing in Dade County,
Florida. The canopy is rounded and dense, with a width approximately
equalling its height. The tree retains its leaves throughout the year
and has an attractive appearance at all times.
The
leaves are
simple, elliptic to elliptic-ovate, 3-6 inches long, with a stiff,
leathery texture, acuminate tips and entire margins. They are shiny and
dark green on the upper surface and dull medium green on the lower
surface; both surfaces are glabrous. The stems, leaves and green fruits
exude a white, sticky latex when they are cut or broken.
The
yellowish male and female flowers are borne in solitary, axillary,
obovoid, separate inflorescences on the same tree. The minute flowers
are joined and the inflorescence develops into a multiple fruit, a
syncarp. Flowering occurs from May to July.
The
fruit have a
diameter of 1.5-2 inches and a weight of 0.5-1.5 oz. Fruit shape is
irregular, being globose, ovate, or oblate. The skin is thin and easily
broken. it is yellow at ripeness and covered with a fine, soft, short
pubescence. The pulp is orange-red to red, very soft and tender, with a
pleasant subacid flavor. The fruit ripens from August to October. No
yield records are available, but mature trees have the capability of
producing 2000 fruit or more per year.
The fruit
have 1-7 seeds,
the number apparently affecting the size and shape of the fruit.
Isolated trees often bear many small, seedless fruit, suggesting that
the tree is self-incompatible and needs cross-pollination to produce
viable seed and fruit of normal size. The seeds are whitish and ovoid,
with a diameter of 0.3- 0.4 inch.
Propagation has
been done in
Florida entirely by seed. Seed take several weeks to germinate and the
young plants grow slowly. No research has been done on cultivar
selection or vegetative propagation in Florida.
CULTURAL REQUIREMENTS
The
observations in this section have been made on kwai muk trees growing
at various locations in Southern Florida.
Soils
The
tree is well adapted to most Florida soils. It grows especially well in
the mildly acid sandy soils and maintains a dark green leaf color
throughout the year (3). Trees grow relatively well in the limestone
soils also (7), but sometimes have leaf chlorosis from deficiencies of
iron, zinc and manganese. The problem is most likely to occur in young
trees, disappearing as the trees attain larger size and a greater
distribution of roots. The deficiencies are easy to correct with foliar
sprays of zinc and manganese and soil applications of iron chelates. No
other research has been done on fertilizer requirements. Trees grow
well when maintained on a fertilizer program such as that used for
citrus trees in home gardens.
Water
The
tree grows best in well-drained soils, but will survive brief flooding
of the root system without apparent injury. For best growth young trees
should be irrigated during hot weather at times when rain does not
occur for several days. Well-established trees appear to need
irrigation under Florida conditions only during extended dry periods,
which can cause leaf drop and limb dieback if the trees do not receive
water.
Temperature
Cultivation
of the kwai muk is limited to the warm parts of southern peninsular
Florida because of susceptibility to freeze injury. Young trees have
leaf and branch injury at air temperatures of 28-30°F and are
likely to be killed at lower temperatures. Large trees survive brief
exposure to air temperatures of 25- 26°F with injury only to leaves
and small twigs, but are damaged severely or killed by temperatures in
the low 20s (4,5,8). Mature trees at Homestead survived the worst
freezes of recent decades. In 1958 and 1977, with only damage to leaves
and small branches (4,5). Trees growing in Central Florida were killed
in the 1962 freeze, when air temperatures reached 20°F or below (8).
Pests and Diseases
No
pests or diseases are recognized at this time as causing significant
damage to kwai muk trees in Florida. It should be recognized, however,
that existing plantings consist of only a few trees growing at widely
separated locations, a situation not conducive to the development of
pests and diseases. This situation could change if large plantings were
made.
Spacing
and Pruning
The
tree grows and fruits best in full sun. Mature trees have canopies with
a diameter of 20-25 ft, so for best results they should be given that
much space in garden or orchard plantings. Shading of the canopy
invariably reduces fruit production. Trees grown in light shade will
still have attractive dark green leaves, but will not have as compact a
canopy as trees grown in full sun.
The tree develops
a
symmetrical, compact canopy without pruning. Pruning is necessary only
to remove dead branches or to decrease the height or width of the tree.
Uses of the Tree and Fruit
The
kwai muk tree is slow-growing and relatively small. The canopy develops
an attractive shape without pruning. The tree retains its dark green
leaves throughout the year and leaf drop is very light. These
characteristics make the tree a good one for landscaping of small urban
properties.
The fruit must be completely ripe for
fresh
consumption; unripe fruit exudes a white, sticky latex when the skin is
broken. The ripe fruit has an excellent flavor and is good for fresh
consumption in the local production area. The fruit has best quality
when ripened on the tree, but it also can be harvested in the mature
green stage and ripened at room temperature. Mature-green fruit ripens
in 1-3 day, so shipping would be difficult. No experiments have been
reported on storage of this fruit.
The fruit can be
preserved
with salt, with sugar syrup or by drying. The dried fruit has a good
texture and flavor (B.A. Campbell, Homestead, personal communication).
CONCLUSIONS
The
kwai muk is well adapted to the environment of southern Florida. The
tree is small and attractive an lends itself well to landscaping on
small urban properties. The tree bears a good, useful fruit and
deserves to be more widely grown in Florida.
LITERATURE
1.
Anonymous. 1928. Plant material introduced by the office of foreign
plant introduction. U.S. Dept. Agr. Inventory No. 86:9.
2.
Bailey Hortorium Staff. 1976, Hortus Third, p113. Macmillan Co. New
York.
3.
Campbell, C.W., J. Popenoe, and H.Y. Ozaki, 1962. Adaptation trials of
tropical and subtropical fruits on sandy soils in Broward County,
Florida. Proc. Fla. State Hort.Soc.75:361-363.
4.
Campbell, C.W., R.J. Knight, Jr. and N.L. Zareski. 1977. Proc. Fla.
State Hort. Soc.90:254-257.
5.
Ledin, R.B. 1958. Cold damage to fruit trees at the Subtropical
Experiment Station, Homestead. Proc. Fla. State Hort. Soc. 71:341-344.
6.
Merrill, E.D. 1929. Unrecorded plants from Kwangtung. Lingnan Sci. J.
8:302-303.
7.
Mowry, H., L.R. Toy, and H.S. Wolfe. 1958. Miscellaneous tropical and
subtropical Florida fruits, Fla. Agr. Ext. Servo Bul. 156A:26-28.
8.
Snow, R.E. 1963. Cold tolerance observations during the 1962 freeze.
Proc. Fla. State Hort. Soc.76:374-377.
Carl
W. Campbell*
University of Florida IFAS,
Tropical
Research and Education Center, Homestead, FL 33031
Proc.FlaState
Hort.Soc.97:318-319 1984.
*
This article is printed by special permission from the author, from
Proceedings of the Ninety Seventh Annual Meeting, Florida State
Horticultural Society, Volume 97, 1985.
Extract from RFCI
Miami Newsletter Aug. 1985
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