Carissa is a genus of about 8 species of shrubs or small trees native to tropical and subtropical regions of Africa, Australia and Asia. Until recently about 100 species were listed, but most of them have been relegated to the status of synonyms or assigned to other genera, such as Acokanthera.^[2]

Description

Conkerberry (C. spinarum) flowers in Shamirpet, Rangareddy district, Andhra Pradesh, India.

Different species of Carissa grow as shrubs or trees, attaining respective heights of 2 to 10 m tall. They bear smooth, sharp thorns that often are formidable; they are true botanical thorns, being modified branches, morphologically speaking. The thorns may be simple, as in Carissa spinarum, dichotomously forked as in Carissa bispinosa, or dichotomously branched as in Carissa macrocarpa.

The leaves are a rich, glossy, waxy green, smooth, simple, entire and elliptic to ovate or nearly lanceolate. They are 2–8 cm long, partly depending on the species, and generally are thick and leathery. In suitable climates some species flower through most of the year. The flowers are nearly sessile, 1–5 cm diameter, with a five-lobed white or pink-tinged corolla. They may be solitary or borne in clusters in an umbel or corymb.^[3] The flowers of some species some have a fragrance reminiscent of Gardenia, which adds to their popularity as garden plants. The fruit is a plum-like berry in the shape of a prolate spheroid, like that of a rugby ball. In colour they vary according to species. The young fruit are green, turning red. In some species they still are red when ripe, whereas others turn a glossy purple-black. Typically they are 1.5–6 cm in length, and usually contain 1-4 flat brown seeds, but up to 16 in some species.

Fruit

The green fruit is poisonous, sometimes dangerously so. The ripe fruit are edible but may be fairly tart, and taste like a giant cranberry, though some species have fruity flavours with overtones of strawberry or apple. They are said to be rich in Vitamin C, calcium, magnesium and phosphorus. The fruit of C. macrocarpa are especially relished and eaten raw or used to make jelly. Various birds eat Carissa fruit and distribute the seed. If eaten before fully ripe, a bitter, poisonous latex is released from the skin. Other than the ripe fruit, the plant is poisonous, much like the related and dangerously poisonous genus Acokanthera.

Carissa carandas is grown in several Asiatic countries for its fruit, which is variously used in cooking and in folk medicine (see article).

Horticulture

Carissa species generally respond well to gardening and are valued in topiary and in forming strong, dense, decorative, thorny, flowering hedges. Some sprawling varieties are useful as ground covers.^[4] Carissa species are grown from seed or cuttings and tolerate slight frost.

Recognised species

Carissa bispinosa, thorns and flowers

The following species are recognised as current and valid.^[5][2]

Formerly placed in this genus

• Acokanthera oblongifolia (Hochst.) Codd (as C. oblongifolia Hochst.)
• Acokanthera schimperi (A.DC.) Benth. & Hook.f. ex Schweinf. (as C. schimperi A.DC.)^[5]

References

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