Huernia macrocarpa
| Light | Bright, filtered light; some direct sun with protection from harsh midday heat |
|---|---|
| Water | Moderate in the growing season; keep dry and cool in winter |
| Soil | Fast-draining, gritty mineral mix (see Soil and potting mix) |
| Temperature | Keep above about 5 °C; frost-tender, roughly USDA zones 10–11 |
| Propagation | Stem cuttings (easy); seed |
| Toxicity | Generally regarded as non-toxic, though the sap may irritate sensitive skin and eyes |
Huernia macrocarpa is a low, clump-forming stapeliad succulent native to the highlands of Ethiopia and the mountains of the Arabian Peninsula. It is grown for its distinctive star-shaped flowers, which are usually a deep, glossy red-brown, and it is offered in a number of regional colour forms that vary from near-black to yellow and pale cream. Like other members of the dogbane and milkweed family Apocynaceae, it belongs to the group of carrion-scented flowers ("carrion flowers") popular with succulent collectors.
Description
Huernia macrocarpa forms low, spreading clumps of short, upright stems that branch freely from the base. The stems are green to grey-green, often flushed reddish or purplish in strong light, and are marked with several blunt angles lined with soft, tooth-like tubercles rather than true spines. In habitat the clumps stay compact and creep across rocky ground; in cultivation they mound up and spill attractively over the edge of a pot.
The flowers appear near the base of young stems, mostly from late summer into autumn. Each is a fleshy, five-pointed star, typically deep red-brown to maroon and often glossy, with a raised ring (the annulus) around the central mouth. As with many stapeliads the blooms give off a faint, unpleasant, fly-attracting odour that helps with pollination, though it is usually much milder than in the larger Stapelia species. The specific epithet macrocarpa ("large-fruited") refers to the paired, horn-like seed pods that follow successful pollination.
Distribution and habitat
The species has a disjunct range spanning the Horn of Africa and southwestern Arabia. It occurs in the Ethiopian highlands and extends across the Red Sea into the mountains of Yemen and southwestern Saudi Arabia. Throughout this range it grows in dry, rocky habitats — on cliff ledges, among boulders and in the shelter of shrubs — where its low clumps root into shallow, gritty pockets of soil and are shaded by surrounding vegetation during the hottest part of the day.
Across such a wide and broken range the species is variable, and several named varieties and regional forms have been described that differ mainly in flower colour and stem robustness.
Cultivation
Huernia macrocarpa is one of the easier stapeliads and a good choice for a grower new to the group. Plant it in a very free-draining, mostly mineral mix in a shallow pot, and give it bright light with some protection from the most intense midday sun — a little shade keeps the stems plump and green rather than shrivelled and sun-stressed.
Water moderately through the warm growing months, letting the mix dry out between waterings, and then keep the plant nearly dry through winter. Cool, dry winter rest reduces the risk of rot and helps trigger the following season's flowers. Good airflow and warmth above about 5 °C suit it best; it is frost-tender and is normally grown under glass or as a houseplant in cool climates. See Watering and Repotting for general technique.
Propagation
The species is very easily raised from stem cuttings. Remove a healthy segment, let the cut surface dry and callous for a few days, then set it on a barely moist, gritty mix; roots form quickly in warm conditions. This is the usual way to bulk up plants and to keep a particular colour form true. It can also be grown from seed when the horned pods ripen and split, though seedlings may not match the parent's flower colour. See Propagation — cuttings for a full walkthrough.
Cultivars and forms
Rather than formal cultivars, H. macrocarpa is best known for its many regional and colour forms, reflecting its variable wild populations. Alongside the typical dark red-brown flowered plants, growers circulate forms with almost black, brick-red, yellow and pale cream flowers, as well as varieties differing in stem size and tubercle shape. Because these forms come more or less true only from cuttings, most are maintained vegetatively in collections.
Common problems
- Rot — the commonest cause of loss, almost always from overwatering, a slow-draining mix or a cold, damp winter; affected stems turn soft, translucent and brown. Remove healthy tips as insurance cuttings at the first sign.
- Shrivelling and discolouration — underwatering or fierce, unshaded sun causes the stems to pucker and redden; adjust watering and light accordingly.
- Pests — mealybugs (white fluff between the tubercles and at the roots) and, in dry stagnant air, spider mites are the usual culprits. See Pests and diseases.
See also
- Huernia — the genus overview
- Stapelia — a related carrion-flower genus
- Propagation — cuttings · Soil and potting mix · Watering · Pests and diseases