While its scented fruit is not of
great value for eating out of hand, the umkokolo, often called in
English kei-apple, is a useful and interesting plant. It is unexcelled
for hedges in regions where the temperature does not commonly fall
below 20° above zero.
The native home of the species is on the
Kei River in South Africa. It is a tall vigorously-growing shrub, with
rich green foliage and long, stiff, sharp thorns. The leaves are
oblong-obovate, about 2 inches in length, often in small clusters at
the bases of the thorns. Staminate and pistillate flowers are produced
on separate plants, and both are without petals. The fruit is oblate or
nearly round, bright golden yellow, and about 1 inch in diameter. The
thin skin incloses a yellow, melting, juicy pulp and five to fifteen
flattened pointed seeds. The flavor is aromatic, highly acid unless the
fruit is fully ripe.
Because of this, the fruit is most commonly used to make jam and preserves.
Outside
of its native region the umkokolo has been planted to a limited extent
along the shores of the Mediterranean in France, Algeria, and Italy; in
northwestern Australia; and in Florida and California. In Florida it is
said to have succumbed to the cold during the severe winter of
1894-1895, and in California it has been killed by temperatures of 16°
above zero. The usual winter temperatures in the southern parts of both
states, however, are too high to injure it, and the species can be
grown safely as far north as the Lake region in central Florida and
favored sections of the San Joaquin Valley in California.
Botanically the umkokolo is a
Dovyalis (latterly written
Doryalis), and it is sometimes listed as
Aberia caffra,
Harv. & Sond. Umkokolo is one of the vernacular names of its native
region in South Africa. The name kei-apple is often spelled incorrectly
kai-apple. The plant is not exacting in its cultural requirements, and
is decidedly drought-resistant. It is most successful in a subtropical
climate, and on a soil rich in humus.
Fig. 59. The umkokolo or kei-apple (Dovyalis caffra) is
a large thorny shrub from South Africa, excellent for hedges. (X 1/2)
It
is considered one of the best hedge plants in South Africa, since its
long sharp thorns make it impenetrable. To form a hedge the bushes
should be set 3 to 5 feet apart, and should be trimmed on both sides
once a year. For the production of fruit, they should not be set closer
than 12 to 15 feet, and both staminate and pistillate plants must be
present. One of the former (male) is considered to be sufficient for
twenty to thirty of the latter (female). If sufficient seedling plants
are grown so that there are sure to be some of both sexes, satisfactory
results will be obtained; otherwise, it is best to propagate staminate
and pistillate plants by layering or some other vegetative means, and
to plant no more staminates than will be required to furnish pollen.
In
the Mediterranean region and in the United States, the plants flower in
April and May and ripen their fruit from August to October. Seeds may
be sown in pans or flats of light sandy loam. Plants propagated in this
manner will begin to bear when four or five years old. Propagation by
layering is practiced in Queensland, and the species will probably lend
itself to shield-budding, since P. J. Wester has shown that another
member of the same genus can be propagated readily in this way. The
ripe fruit is sometimes attacked by the Mediterranean fruit-fly (
Ceratitis capitata Wied.).