Duvalia

Duvalia is a genus of small, low-growing stapeliad succulents in the milkweed family Apocynaceae, native to Africa and the Arabian Peninsula. Its plants form low clumps of short, soft, tuberculate stems, and produce flat, star-shaped flowers whose most distinctive feature is a fleshy, raised central disc (an annulus) sitting in the middle of the bloom. Like their relatives among the stapeliads, Duvalia flowers are fly-pollinated and often carry a faint carrion scent that rewards a close look far more than a close sniff.

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Description

Duvalia species are among the smallest and most modest of the stapeliad group. The stems are short, plump and few-angled, usually carrying soft, blunt tubercles (rather than true spines) along their ribs, and they range from grey-green to purplish depending on light and stress. Rather than growing tall, the stems tend to sprawl and root where they touch the ground, so a happy plant slowly builds up into a low, spreading mat or cushion.

The flowers are the reason growers keep them. Each is a flat, five-lobed star, often with narrow, sometimes reflexed lobes that can be dark maroon, chocolate-brown, purplish or reddish, and frequently finely wrinkled or hairy. At the centre sits the raised, fleshy disc — a cushion-like annulus surrounding the reproductive column — which is the easiest single feature for telling Duvalia apart from lookalike genera such as Duvaliandra, Piaranthus and the larger Stapelia. As with other stapeliads, the blooms are pollinated by flies and may give off a mild carrion odour.

Distribution

The genus is centred on southern Africa, with a strong presence in South Africa and Namibia, and further species scattered north and east through tropical Africa into the Arabian Peninsula. Plants typically grow in dry, open country — among rocks, in the shelter of low shrubs, or tucked into gritty and sandy soils where their small stems are easily overlooked until the flowers appear.

Notable species

Duvalia caespitosa — a widespread, clump-forming South African species with dark reddish stars.
Duvalia corderoyi — compact, freely clumping, and one of the more commonly grown in collections.
Duvalia elegans — noted for its neatly starred, slender-lobed flowers.
Duvalia modesta — a small, modest species true to its name, easy in cultivation.
Duvalia polita — with smooth, glossy flower lobes.
Duvalia sulcata — the main representative reaching into Arabia, with grooved stems.

Cultivation

Duvalia are grown much like other stapeliad succulents and are generally undemanding once their one weakness — wet, cold roots — is respected. Give them a very free-draining, mostly mineral mix in a shallow pot, since the stems are shallow-rooted and resent staying soggy. Bright light suits them well, though a little shade from the harshest afternoon sun keeps the stems from scorching and helps them hold good colour without shrivelling.

Water regularly through the warm growing season, always letting the mix dry out between drinks, and then keep the plants dry and cool through winter. Cold, damp conditions are the classic killer: stems soften, blacken and collapse at the base if kept wet in the cold. Because they clump low and root as they spread, Duvalia do well in wide, shallow containers and appreciate repotting into fresh gritty mix every couple of years. See Watering for general technique.

Propagation

Being clumping, low growers, Duvalia are very easy to increase from stem cuttings or by dividing an established clump. Detach a healthy stem or rooted offset, let the cut surface dry and callus for a few days, then set it on a barely moist mineral mix; roots usually form quickly in warm weather. They can also be raised from seed where the distinctive paired, horn-like stapeliad seed pods ripen, though seed is less commonly used than simple division. See Propagation - offsets for handling clumps.

Hobby and cultivar notes

Duvalia are prized by stapeliad enthusiasts more as a curious, easy-to-grow genus than as a source of named cultivars, of which there are few. Because the plants are small and clump readily, they are popular for compact collections and windowsill growing, and they cross and intergrade freely enough that both natural and garden hybrids occur within the genus and with close relatives. Grafting is generally unnecessary given how easily the stems root on their own. For growers building a stapeliad collection, they pair naturally with genera such as Stapelia, Huernia, Piaranthus and Orbea.

References

Horticultural information for growing these plants as ornamentals. Always confirm plant identification and any handling, grafting, or safety advice against authoritative sources before acting.