Adenium obesum

Common name: Desert rose

Other common names: Mock azalea

Description

Desert Rose is a flowering succulent originating from dry areas of Sub-Saharan Africa and Arabia, and is a close relative of Frangipani (Plumeria ruba) and Oleander (Nerium oleander).

It grows slowly to heights of up to 6 m (20 ft) under ideal conditions, though is more commonly 1 to 2 m (3 to 6 ft) tall and has a shrub-like appearance. The stems are soft wooded and the trunk swollen at the base, adding to the plant's ornamental appeal.

The leaves are dark green, club-shaped, rounded at the tip and tapered toward the base, attaching directly to the branches. They are few in number, especially in the dry season when they fall off the plant, leaving the branches mostly bare.

Flowering is at its fullest in the dry season, however on-and-off flowering is common the rest of the year in regularly watered gardens. The flowers are monoecious, with separate female and male flowers on the same plant. They are very showy and as a result of selective breeding come in a range of colours from from red to dark or light pink, yellow, pure white or white with pink margins, depending on the variety or hybrid.

Fruiting is irregular with no fruiting in some years. When the plant does fruit, they are slender, curved seedpods with small cylindrical, hairy tufted seed inside, designed for wind dispersal.

Use

It is mostly cultivated as a container or specimen plant for its showy floral display and for the unusual, sometimes curious shapes the trunk develops. It is a good performer in seaside gardens, on account of its tolerance to light salt spray and is a suitable plant for poolsides and Bonsai, doing especially well in a container or pot as this provides the fast drainage it needs.

Climate

Although naturally adapted to dry climates, Desert Rose tolerates humidity and will grow and flower reliably in dry to humid subtropical and tropical climates, generally in areas with annual lows of 11 to 25 °C, annual highs of 20 to 35 °C, annual rainfall of 200 to 2300 mm and a dry season of 10 months or less.

How to grow

New plants are easily grown from seed or cuttings. Seed grown plants start flowering in the second year, a year or two earlier than vegetatively grown plants. It performs best on quick-draining sand and sandy loam soils of a slightly acid to moderately alkaline nature, generally with a pH of 6.5 to 8.0 and on sites with full to partial-sun exposure.

Problem features

It is unlikely to become a weed due to its shy seeding habit and there does not appear to be any record of it anywhere as a serious weed. It is assessed as a low weed risk species for Hawaii by the Hawaii Pacific Weed Risk Assessment project (HPWRA)

The sap is highly poisonous and has a long history of use as an arrow poison in its native range.

Where it will grow


References

Books

  • Barwick, M., et al. 2004, Tropical & subtropical trees : a worldwide encyclopaedic guide, Thames and Hudson, London

  • Perry, F. & Hay, R. 1982, A field guide to tropical and subtropical plants, Van Nostrand Reinhold Company, New York

  • Polunin, Ivan 1987, Plants and flowers of Singapore, Times Editions, Singapore

  • Randall, R. P. 2007, The introduced flora of Australia and its weed status, Cooperative Research Centre for Australian Weed Management, Glen Osmond, South Australia

  • Rauch, F. D. & Weissich, P. R. 2000, Plants for tropical landscapes : a gardener's guide, University of Hawaii Press, Honolulu

  • Schmelzer G.H., et al. 2008, Plant Resources of Tropical Africa, Volume 11(1) : Medicinal Plants 1, PROTA Foundation, Backhuys Publishers, Leiden

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