Adenium somalense
| Light | Full sun; the more the better for compact growth and flowering |
|---|---|
| Water | Regularly in active growth, allowing the top of the mix to dry; keep nearly dry during winter dormancy |
| Soil | Fast-draining gritty mineral mix (see Soil and potting mix) |
| Temperature | Warmth-loving; keep above about 10 °C, no frost (USDA zones 11–12) |
| Propagation | Seed (keeps the tall trunk habit); cuttings and grafting also used |
| Toxicity | Toxic — the milky sap contains cardiac glycosides; keep away from pets and children |
Adenium somalense is a tall, fast-growing desert rose from the Horn of Africa, forming a distinctly conical trunk that can become tree-like with age. It is one of the larger and more upright members of the genus Adenium, and its vigour and readiness to bloom have made it a favourite parent in the world of desert-rose hybridizing.
Description
Adenium somalense builds a swollen, tapering caudex that broadens at the base and narrows upward into a slender trunk, giving mature plants a bottle- or spindle-shaped silhouette. In the ground and given time it can reach several metres tall, far larger than the squat Adenium obesum most growers know, though potted specimens stay much smaller. The bark is smooth and pale grey-green, and the branches carry glossy, narrow leaves — often with pale veins — toward their tips.
The flowers are relatively small and star-shaped, with narrow, pointed petals; they are typically pink to red, usually paler in the throat and darker toward the petal margins, with prominent nectar guides, and are borne in flushes over a long season when the plant is warm and in strong light. Like all adeniums it is deciduous or semi-deciduous, dropping some or all of its leaves during a cool or dry rest.
Botanically the plant is variable and its rank is contested: it has been described as a species (Adenium somalense) and also treated as a subspecies of Adenium obesum (as A. obesum subsp. somalense). Major authorities such as Plants of the World Online currently treat it as a synonym of a broadly defined Adenium obesum, though the name somalense remains in wide use among growers.
Distribution and habitat
The species is native to the Horn of Africa and adjacent East Africa — Somalia, Ethiopia, Kenya and Tanzania — where it grows in hot, seasonally dry bushland and on rocky slopes. It endures long droughts by storing water in its trunk and roots and by shedding its leaves, then leafing out and flowering when the rains return. This background explains its two golden rules in cultivation: abundant heat and light, and sharp drainage.
Cultivation
Adenium somalense is grown much as other desert roses, but rewards the extra warmth and sun its origins suggest. Plant it in a very free-draining, mostly mineral mix in a pot with generous drainage, and give it the brightest position available; weak light produces soft, stretched growth and few flowers. During the warm growing season water thoroughly whenever the mix has begun to dry, then let it approach dryness again — the plant grows quickly and drinks more than a slow globular cactus would. As temperatures fall, taper off and keep it nearly dry through its winter rest, which also protects the fleshy roots from rot.
Because this species naturally makes a tall, trunk-forming plant, some growers prune the top to encourage branching and a fuller crown. Feed lightly during active growth, and see Watering and Repotting for general technique. All parts exude a toxic milky latex when cut, so wash your hands after pruning and keep the plant out of reach of pets and children — see Pests and diseases for related care notes.
Propagation
Seed is the preferred method and the one that preserves the characteristic swollen, conical trunk, since seed-grown plants develop a fat caudex from the base. Sow fresh seed on a warm, gritty surface and keep it lightly moist until germination, which is usually quick in heat; see Propagation — seed.
The species can also be grown from cuttings, though cutting-grown plants tend to make a woodier, less bulbous base. Grafting is widely used in the hobby to combine a vigorous rootstock with a choice flowering top, and is especially common for named hybrids.
Cultivars
Adenium somalense features prominently in modern desert rose breeding. Its vigour, tall habit and free flowering are frequently crossed into Adenium obesum and multi-species hybrids to add size, stem character and bloom power. Named selections and complex hybrids are traded widely; see the Adenium genus page for an overview of the hybrid groups.
Common problems
- Rot — the most frequent killer, caused by cold, wet mix or overwatering during dormancy; the caudex or roots soften and turn brown.
- Etiolation — too little light gives weak, elongated stems and poor flowering.
- Pests — mealybugs (white fluff in leaf axils and on roots), spider mites and aphids on new growth are the usual offenders.
See also
- Adenium — the genus overview
- Adenium obesum — the closely related common desert rose
- Grafting · Soil and potting mix · Watering · Propagation — seed · Propagation — cuttings