THE GENUS PERESKIA.
(Named in honour of Nicholas F. Peresk, a botanist of Provence.)
The thirteen species included in the genus Pereskia differ so markedly
from all other kinds of Cactus, that at first sight one can scarcely
believe they are true Cactuses, closely related to Cereus and
Epiphyllum. They have erect or trailing stems and branches, and usually
form dense, large bushes; the branches are woody and thin, and bear
large, laurel-like leaves, which remain on the plants several years--so
that they may be termed evergreen. They have, however, the
spine-cushions, the tufts of woolly hair and stout spines, and the
floral characters which distinguish Cactuses from other plants; they are
also succulent, the leaves and young branches being soft and fleshy.
They appear to have the same peculiar provision for enabling them to
bear long periods of drought without suffering that characterises the
more familiar forms of Cactuses. The development of the spines in this
genus is different from what takes place in all other spiny plants of
this order. In the latter the spines are stoutest and most numerous on
the younger parts of the plant, the older or woody parts being either
spineless, through having cast them, or much less spiny than when they
were younger. Thus, in Opuntia we find few or no spines on the old parts
of the stems of even such species as O. horrida, O. nigricans, &c. In
Echinocactus, too, the spines about the base of old plants are much
fewer, if not entirely cast off, than on the upper part. In Pereskia the
contrary is the case. Taking P. aculeata as an example, this is best
known in gardens as having branches about as thick as a goose-quill,
with ovate leaves, at the base of which there is a pair of curved
spines, ¼ in. long, and shaped like cats' claws. But this plant when it
gets old has a stem 3 in. in diameter, and clothed down to the ground
with cushions of spines fixed firmly in the bark, each cushion composed
of from twenty to fifty spines, and each spine 1 in. or more in length.
From two to six new spines are developed in the centre of each healthy
cushion annually. It would be absolutely impossible for any animal to
climb an old stem of a Pereskia. In P. Bleo the spines are 2 in. long,
and the cushions are much larger.
The flowers of Pereskias are borne singly or in panicles, at the ends of
the young, ripened branches. In shape, each flower may be compared to a
single Rose, the petals being flat and spreading, and the numerous
stamens forming a compact cluster in the centre. The stigma is erect,
and divided at the top into four or more rays. The fruit is a berry
shaped like a Gooseberry, and covered with minute clusters of short
bristles.
All the species are found in tropical America and the West Indies.
Cultivation.--Although several of the kinds of Pereskia are
sufficiently ornamental to be deserving of a place in gardens as
flowering plants, yet they are rarely cultivated--in England, at least
--for any other purpose than that of forming stocks upon which
Epiphyllums and other Cacti are grafted. Only two species are used,
viz., P. aculeata and P. Bleo, the former being much the more popular of
the two; whilst P. Bleo, on account of the stoutness of its stems, is
employed for only the most robust kinds of grafts.
Propagation.--Both the above-named species may be propagated to any
extent, as every bit of branch with a leaf and eye attached is capable
of rooting and soon forming a stock. The practice among those who use
Pereskias as stocks for Epiphyllums is as follows: Cuttings of P.
aculeata are planted in sandy soil, in boxes, and placed on a shelf in a
stove till rooted. In about a month they are ready to be planted singly
in 3 in. pots, any light soil being used; and each plant is fastened to a
stake 1 ft. long. They are kept in a warm, moist house, all lateral
shoots being cut away, and the leader encouraged to grow as tall as
possible in the year. From December the plants are kept dry to induce
the wood to ripen, preparatory to their being used for grafting in
February. Stocks 9 in. or 1 ft. high are thus formed. If taller stocks are
required, the plants must be grown on till of the required length and
firmness. Large plants may be trained against a wall or along the
rafters in a warm house; and when of the required size, the branches may
be spurred back, and Epiphyllums, slender Cereuses, and similar plants,
grafted upon them. In this way very fine masses of the latter may be
obtained in much less time than if they were grown from small plants.
SPECIES.
P. aculeata (prickly); West Indian or Barbados Gooseberry.--Stem woody,
more or less erect, branching freely, and forming a dense bush about
6 ft. high. Young branches leafy; old ones brown, leafless, clothed with
large cushions of long, stout, brown spines, sometimes 2 in. in length.
Leaves alternate, with very short petioles, at the base of which is a
pair of short spines, and a small tuft of wool in the axil; blade 3 in.
long by 2 in. broad, soft, fleshy, shining green. Flowers
semi-transparent, white, in terminal panicles; sepals and petals ¾ in.
long by ¼ in. wide; stamens in a large, spreading cluster, white, with
yellow anthers. Ovary covered with small cushions of short bristles,
with sometimes a solitary spine in the centre of each cushion. Fruit
1 in. long, egg-shaped, red, edible. There is a large plant of this in
the Succulent House at Kew which flowers almost annually, but it has
never ripened fruits. In the West Indies it is a very common shrub,
whilst at the Cape of Good Hope it is used for fences--and a capital
one it makes.
P. a. rubescens (reddish).--This variety has narrower, longer leaves,
which are glaucous-green above and tinged with red below; the spines on
the old stems are shorter and more numerous in each cushion. This
requires the same treatment as the type.
P. Bleo (native name); Fig. 87.--A stout, branching shrub, having an
erect stem, 3 in. or more in diameter, with green bark and very large
cushions of spines; cushion a round, hard mass of short, woolly hair,
from which the spines--about fifty in each cushion--radiate in all
directions; longest spines 2 in. or more in length; one or two new ones
are developed annually, and these are bright red when young, almost
black when ripe; young branches ¼ in. to ½ in. in diameter. Leaves ½ in.
apart, 3 in. to 6 in. long by 1 in. to 2 in. wide, oblong, pointed, with
short petioles, and a small tuft of short, brown hair, with three or
more reddish spines, in the axil of each. Flowers on the ends of the
young, ripened branches, clustered in the upper leaf-axils, each flower
2 in. across, and composed of a regular circle of rosy-red petals, with a
cluster of whitish stamens in the centre. They remain on the plant
several weeks. Native of New Grenada. Probably P. grandiflora is the
same as this, or a slightly different form of it. A large specimen may
be obtained in a year or two by planting it in a well-drained bed of
loam, in a warm, sunny house. It blossoms almost all summer if allowed
to make strong growth. Pretty little flowering plants may be had by
taking ripened growths from an old plant, and treating them as cuttings
till rooted. In the following spring they are almost certain to produce
flowers. Plants 1 ft. high, bearing a cluster of flowers, are thus
annually obtained at Kew. Fig. 87 represents a short, stunted branch,
probably from a specimen grown in a pot. When planted out, the leaves
and spine-cushions are farther apart.
[Illustration: FIG. 87. PERESKIA BLEO.]
P. zinniaeflora (Zinnia-flowered); Fig. 88.--Stem erect, woody,
branching freely, the branches bearing oval, acuminate, fleshy,
wavy-edged, green leaves, with short petioles, and a pair of spines in
the axil of each. Spine-cushions on old stems crowded with stout, brown
spines. Flowers rosy-red, terminal on the ripened young shoots, and
composed of a whorl of broad, overlapping petals, with a cluster of
stamens in the centre, the whole measuring nearly 2 in. across. This
species is a native of Mexico; it grows and flowers freely if kept in a
warm house.
[Illustration: FIG. 88. PERESKIA ZINNIAEFLORA.]