Adenium arabicum
| Light | Full sun; the more light, the fatter and more compact the caudex |
|---|---|
| Water | Generous in warm active growth, allowing the mix to dry between; keep dry and warm during winter dormancy |
| Soil | Very free-draining, gritty mineral mix |
| Temperature | Warmth-loving; protect from any frost, ideally kept above 10 °C |
| Propagation | Seed (for the best caudex); cuttings possible but rarely swell as dramatically |
| Toxicity | Toxic — sap contains cardiac glycosides; keep away from pets and children |
Adenium arabicum is a fat-bodied desert rose native to the Arabian Peninsula, prized by growers for its broad, low-branched swollen caudex. Once treated as a subspecies of the common desert rose, it is distinguished by its stout, spreading, often multi-headed base that lends itself beautifully to a bonsai-like style of cultivation. It belongs to the genus Adenium in the family Apocynaceae, the same family as the oleanders and frangipanis.
Description
Adenium arabicum is a caudiciform succulent shrub, meaning it stores water in a greatly thickened basal trunk. Compared with the more upright Adenium obesum, arabicum tends to be squatter and wider, forming a broad, buttressed caudex that branches close to the ground into several stout stems rather than a single tapering trunk. In good conditions the base can swell to an impressive girth, taking on a fluted, muscular appearance that is the plant's chief ornamental appeal.
The leaves are broad, leathery and somewhat rounded, often larger and more grey-green than those of the common desert rose, clustered toward the branch tips. Plants are typically deciduous, dropping their leaves during the dry, cool season and resting until warmth returns. Pink to rose-coloured trumpet flowers appear on established plants, though the species is grown far more for its form than its bloom.
Distribution and habitat
The species is native to the arid regions of the Arabian Peninsula, including Yemen, Oman and southwestern Saudi Arabia. It grows on rocky slopes, in gritty wadis and among sun-baked outcrops where drainage is sharp and rainfall is seasonal and brief. In habitat the swollen caudex is an adaptation to long droughts, hoarding water and nutrients through months of dry heat.
Cultivation
Adenium arabicum is a rewarding plant for warm, sunny conditions and is popular among enthusiasts who train it in a bonsai-like manner. Grow it in as much direct sun as you can give it — strong light is what keeps the caudex fat and the growth compact rather than lanky. Use a very free-draining, mostly mineral mix, and a pot that is not overly large.
During the warm growing season the plant is thirsty and can be watered generously, but the mix must dry appreciably between waterings; standing wet, especially when cool, quickly leads to rot at the caudex. As temperatures fall the plant naturally drops its leaves and enters dormancy — at this point cut watering right back and keep it warm and dry. Protect it from frost at all times, as it has no cold tolerance. Many growers lift and slightly expose the caudex at each repotting to encourage the characteristic fat, buttressed base. See Watering for general technique.
A note of caution: like all adeniums, the milky sap contains cardiac glycosides and is toxic if ingested. Wash your hands after pruning and keep the plant away from curious pets and children.
Propagation
Seed is the preferred method and the only reliable way to obtain the fat, characterful caudex that makes the species desirable — seed-grown plants develop a swollen taproot base from the start. Sow fresh seed on a warm, gritty surface and keep it lightly moist and humid until germination, which is usually quick in warmth. See Propagation — seed for a full walkthrough.
Cuttings will root, but plants grown from cuttings tend to build a thinner, more shrub-like base rather than the prized bulbous caudex, so they are less favoured for this species. See Propagation — cuttings. Choice forms and heavy-caudex selections are sometimes grafted to preserve their characteristics.
Cultivars
Selective breeding, much of it in Thailand, has produced a range of named arabicum forms selected for exceptionally fat, squat or multi-headed caudices, as well as for flower colour. Well-known groups include broad, low "fat plant" types and various regional selections; because these traits come reasonably true from seed, most are maintained through seed selection rather than cuttings.
Common problems
- Caudex rot — the commonest cause of loss, almost always from overwatering, a poorly draining mix, or watering while cool and dormant; the base softens and discolours.
- Etiolation — too little light produces thin, stretched growth and a disappointingly slim base instead of a fat caudex.
- Pests — mealybugs (white fluff in the leaf axils and on roots), spider mites and occasional scale. See Pests and diseases.
- Cold damage — exposure to frost or prolonged chill causes blackening and collapse; move plants somewhere warm well before winter.
See also
- Adenium — the genus overview
- Adenium obesum — the closely related common desert rose
- Grafting · Soil and potting mix · Watering · Repotting · Propagation — seed · Propagation — cuttings