Piaranthus cornutus
| Light | Bright light with some shade from harsh afternoon sun; too little light makes stems etiolate |
|---|---|
| Water | Sparingly; let the mix dry fully between waterings, and keep dry through winter |
| Soil | Very free-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep well above freezing; frost-tender, USDA zones 10–11 |
| Propagation | Stem cuttings and division of clumps; also seed |
| Toxicity | Not documented as toxic, but not intended for consumption |
Piaranthus cornutus is a small, low-growing stapeliad from southern Africa that spreads into tidy clumps of short, soft, angled stems. It is grown for its curious flat, star-shaped flowers, which are velvety on the inner face and range in colour from cream and pale yellow to brownish tones, spotted and banded with purple, crimson or brown. Like other members of the genus, it belongs to the milkweed family Apocynaceae and is a rewarding, undemanding plant for the succulent collector.
Description
Piaranthus cornutus forms mat-like clusters of short, fleshy stems only a few centimetres tall. The stems are soft, greyish-green to green, and bluntly four-angled with a few tubercle-like teeth along the angles, often turning brownish or bronzed when grown hard in bright light. They branch and root freely at the base, so a healthy plant slowly creeps outward to fill its pot.
The flowers are the main attraction. Borne singly or a few at a time from near the stem tips, they open flat and star-shaped, with five spreading lobes. The back of each lobe is smooth, while the inner face is velvety with minute hairs, and the colouring is variable — pale yellow, cream or brownish, spotted, patched or banded with purple, crimson or brown. As with many stapeliads the blooms are fly-pollinated, but in this species they are scentless or only faintly sweetish rather than strongly carrion-scented like the larger Stapelia.
Distribution and habitat
The species is native to the arid interior of southern Africa, ranging from southern Namibia into the north-western parts of South Africa. Plants shelter among rocks, in gritty or sandy soils, and often nestle beneath low shrubs or in the partial shade of larger plants, which protects the soft stems from the fiercest sun. In habitat they endure long dry spells by shrinking back and relying on their fleshy stems for stored moisture.
Cultivation
Piaranthus cornutus is easy to please as long as its roots are never left wet and cold. Grow it in a very free-draining, mostly mineral mix in a shallow pot or pan that suits its spreading habit. Give it bright light with some protection from scorching afternoon sun; strong light keeps the stems compact and brings out brownish or bronzed tints, while too little causes weak, drawn-out (etiolated) growth.
Water sparingly during the growing season, allowing the mix to dry out completely between waterings, and keep the plant dry and cool through winter to prevent rot — the most common cause of loss in stapeliads. Good airflow helps enormously. See Watering and Repotting for general technique, and lift and refresh clumps every few years as they exhaust the pot.
Propagation
Propagation is straightforward. The easiest method is to take stem cuttings or simply divide an established clump, since the stems root readily where they touch the soil. Allow cut pieces to callous for a day or two, then set them on a barely moist, gritty surface until roots form. Plants can also be raised from seed when the paired, slender seed pods (follicles) ripen and split. See Propagation — offsets for related technique with clumping succulents.
Common problems
- Rot — soft, blackening stems almost always follow overwatering, a slow-draining mix, or cold wet conditions in winter. Remove affected stems and re-root healthy tips.
- Etiolation — pale, elongated, floppy stems indicate too little light; move the plant somewhere brighter.
- Pests — mealybugs (white fluff in the stem angles and at the roots) are the usual nuisance; watch also for aphids on developing flower buds. See Pests and diseases.
See also
- Piaranthus — the genus overview
- Stapeliads and other clumping succulents
- Soil and potting mix · Watering · Propagation — cuttings · Repotting · Pests and diseases