Adenium obesum
| Light | Very bright; full sun once established |
|---|---|
| Water | Regular in active growth; keep much drier during winter rest |
| Soil | Fast-draining, gritty mix (see Soil and potting mix) |
| Temperature | Warmth-loving; keep above about 10 °C, ideally warmer; USDA zones 11–12 |
| Propagation | Seed (produces the swollen caudex); cuttings root readily but rarely form a fat base |
| Toxicity | Toxic — sap contains cardiac glycosides; keep away from pets and children |
Adenium obesum is the classic desert rose, a succulent shrub or small tree famous for its swollen, sculptural trunk (the caudex) topped with glossy leaves and showy trumpet-shaped flowers. Native to the drylands of Africa and Arabia, it is enormously popular in cultivation and is the parent of countless single- and double-flowered hybrids in shades from white through pink to deep red.
Description
Adenium obesum forms a thick, water-storing caudex that swells at the base and tapers into branching stems, giving old specimens the look of a miniature baobab or a natural bonsai. Height and girth vary greatly with age and growing conditions, from a compact potted plant to a substantial shrub in the ground.
The leaves are simple, leathery and often glossy, clustered toward the branch tips and typically shed during the dry season or a cool winter rest. The flowers are the main attraction: five-petalled, funnel- to trumpet-shaped blooms, usually carried in clusters at the stem tips over a long warm-season period. Wild plants tend toward pink with a paler throat, while cultivated forms and hybrids span a wide range of colours, patterns and doubled or ruffled petals.
All parts of the plant exude a milky latex when cut. This sap contains cardiac glycosides and is toxic if ingested; it can also irritate skin and eyes, so wash your hands after pruning.
Distribution and habitat
The desert rose is native to a broad sweep of arid and semi-arid country across the Sahel and East Africa and into the Arabian Peninsula. It grows on rocky slopes, in scrub and in seasonally dry woodland, where it endures long droughts by storing water in its swollen stem and dropping its leaves.
In these habitats the plant experiences intense sun, sharp drainage and a pronounced wet-and-dry seasonal rhythm — conditions worth keeping in mind when growing it.
Cultivation
Adenium obesum is a sun-lover and thrives with as much bright light as you can give it; too little light produces weak, stretched growth and few flowers. Grow it in a very free-draining, gritty mix in a pot with generous drainage, and give it real warmth during the growing season.
Water freely while the plant is in active growth and the soil is drying between waterings, then cut back sharply as temperatures drop. Through a cool winter the plant should be kept much drier and rested; combined with cold, wet soil is the quickest route to a rotted caudex. Protect it from frost — it is not cold-hardy and suffers below roughly 10 °C. Feed lightly during the growing season for steady growth and flowering. Many growers also prune to shape the branching and, over years, lift and expose more of the caudex to emphasise the plant's characteristic bonsai-like form. See Watering and Repotting for general technique.
Propagation
Seed is the preferred method because seed-grown plants develop the fat, tapering caudex that gives the desert rose its appeal. Sow fresh seed on a warm, free-draining surface and keep it lightly moist until germination, which is usually quick in warmth. See Propagation — seed.
Cuttings root fairly readily and are used to reproduce a particular flower colour or a named hybrid true to type, but cutting-grown plants tend to build a thinner, less bulbous base. Desirable double-flowered and patterned cultivars are also commonly grafted onto seedling rootstock, which combines a vigorous root system and a fatter base with the chosen flower. See Propagation — cuttings.
Cultivars
The desert rose has been bred extensively, especially in Thailand and elsewhere in Southeast Asia, for flower colour, form and caudex shape. Named selections and hybrids offer single and double blooms, ruffled or overlapping petals, and colours from pure white and soft pink through vivid red to near-black tones, as well as striped and picotee patterns. Many involve crosses with other Adenium species. Because these forms do not come true from seed, they are maintained by cuttings or grafting.
Common problems
- Caudex and root rot — the most common killer, caused by too much water (especially when cool) or a slow-draining mix; the base softens and discolours.
- Etiolation — too little light leads to thin, elongated stems, sparse leaves and poor flowering.
- Cold damage — exposure to frost or prolonged chill causes blackened, collapsing tissue.
- Pests — mealybugs, aphids on new growth and flower buds, spider mites in hot dry air, and occasionally scale. See Pests and diseases.
See also
- Adenium — the genus overview
- Grafting · Soil and potting mix · Watering · Repotting · Propagation — seed · Propagation — cuttings