Caralluma acutangula
| Light | Bright light to full sun, with light shade in the hottest part of the day |
|---|---|
| Water | Regularly during active growth, always letting the mix dry out between waterings; keep dry and rested in winter |
| Soil | Very free-draining mineral mix (see Soil and potting mix) |
| Temperature | Warmth-loving; keep frost-free, roughly USDA zones 10–11 |
| Propagation | Stem cuttings and division of clumps; also seed |
| Toxicity | No significant toxicity reported; the watery (non-milky) sap may still mildly irritate — keep out of reach of curious pets |
Caralluma acutangula is a clump-forming stapeliad — a leafless, stem-succulent member of the milkweed subfamily in the Apocynaceae — native to dry regions of Africa and the Arabian Peninsula. It is one of the larger, more robust stapeliads, named for its sharply angled stems, and in season carries large umbels of many star-shaped, purple-black flowers typical of its genus. Like other members of Caralluma, it is grown as much for its architectural angular growth as for its curious, briefly-lived blooms.
Description
Caralluma acutangula forms robust clusters of erect succulent stems and is one of the larger stapeliads, the stems ranging from roughly 40 cm to over a metre tall. The stems are conspicuously (3–)4-angled — the sharp, prominent ridges that give the species its name — and are toothed along the angles with prominent, often downward-pointing tooth-like tubercles, soft rather than true spines. Colour ranges from pale or whitish green to grey- or olive-green.
Being a leafless stem succulent, the plant photosynthesises through its green stems; any leaves are reduced to tiny, fleeting rudiments. The flowers appear in large, dense, globose umbels, each bloom star-shaped and roughly 2 cm across, with five broad lobes in velvety purple-black to brownish-black. As with many stapeliads, the blooms carry a strong, foetid carrion scent that attracts flies as pollinators — a normal, if surprising, feature of the group rather than a sign of ill health.
Distribution and habitat
The species ranges across dry country of West and East Africa — from Mali and Mauritania eastward to Ethiopia, Somalia and Kenya — and extends into Egypt and the Arabian Peninsula (Saudi Arabia and Yemen). It is a plant of hot, arid and semi-arid country — rocky slopes, gravelly flats and open deciduous bushland — typically at low elevations. There it grows among rocks and low shrubs that give a little shade and shelter, enduring long dry spells and drawing on brief seasonal rains. Plants often nestle at the base of nurse shrubs, which protect them from the fiercest sun and from grazing.
Cultivation
Caralluma acutangula is grown much like other carallumas and stapeliads, and the same cautions apply: it resents standing wet far more than it resents drought. Grow it in a very open, mostly mineral mix in a pot with generous drainage, and give it bright light — ample sun brings out the best colour and keeps the stems compact, though a little shade at midday in the hottest climates prevents scorch.
Water freely enough to keep the stems plump during active growth in the warm season, always letting the mix dry out well between waterings, then keep the plant nearly dry and warm through winter. Cold, damp conditions are the classic killer of stapeliads. Warmth is appreciated year-round; protect from frost. See Watering and Repotting for general technique.
Propagation
The easiest method is by stem cuttings: detach a segment, let the cut end callus and dry for several days, then set it on a barely-moist mineral mix to root. Established clumps can also be lifted and divided (see Propagation — offsets). Fresh seed will germinate on a warm, gritty surface kept lightly humid, though seed-raised stapeliads are slower and less commonly grown by hobbyists than rooted cuttings. See Propagation — seed for details.
Common problems
- Basal and stem rot — the most frequent cause of loss, almost always from overwatering, a heavy mix, or cold damp conditions; affected stems turn soft, brown or black.
- Mealybugs — white cottony pests that lodge in the stem angles and at the roots; check regularly (see Pests and diseases).
- Etiolation — too little light makes stems thin, pale and floppy, and reduces flowering.
- No flowers — usually from insufficient light or a missing cool, dry winter rest.
See also
- Caralluma — the genus overview
- Stapeliads — the carrion-flower group of the Apocynaceae
- Soil and potting mix · Watering · Propagation — cuttings · Propagation — offsets · Pests and diseases