Delosperma nubigenum
| Light | Full sun to very bright light; tolerates some light shade |
|---|---|
| Water | Moderate in growth; drought-tolerant once established; keep drier in winter |
| Soil | Gritty, sharply draining mix (see Soil and potting mix) |
| Temperature | Exceptionally cold-hardy; survives hard frost, roughly USDA zones 4–9 |
| Propagation | Cuttings and division (primary); also seed |
| Toxicity | Generally regarded as non-toxic to cats and dogs |
Delosperma nubigenum is a very cold-hardy, low-growing ice plant from the high mountains of southern Africa, forming dense mats of small, fleshy, bright green leaves that flush deep red or bronze in cold winter weather. In late spring and early summer the mats are smothered in cheerful, daisy-like yellow flowers, making it one of the easiest and hardiest members of the genus Delosperma for cold-climate rock gardens and containers.
Description
Delosperma nubigenum is a creeping, evergreen succulent that hugs the ground, spreading by trailing stems that root as they go to form a tight, weed-suppressing carpet only a few centimetres tall. The leaves are small, fleshy, somewhat flattened and oval, and bright green through the growing season; as temperatures fall they take on rich red, bronze or copper tones, providing colour right through winter before greening up again in spring.
The flowers are the classic Delosperma form — many narrow, glistening petals radiating around a small central boss — but here a clear, bright yellow. They open in the sun over a long flush from late spring into summer, and can appear sporadically into autumn. The specific epithet nubigenum, meaning roughly "born of the clouds", refers to the misty high-altitude habitat where the species grows.
Distribution and habitat
The species is native to the Drakensberg and other high mountain regions of southern Africa, including Lesotho and the high escarpment of eastern South Africa (Eastern Cape and Free State). It grows at high elevation on rocky slopes, ledges and gritty ground, where it endures cold, snow and sharp seasonal swings. This mountain origin is the source of its remarkable frost hardiness — far greater than that of most succulents — and its preference for excellent drainage combined with more moisture than a desert cactus would tolerate.
Cultivation
Delosperma nubigenum is one of the most forgiving ice plants and an excellent choice for beginners in cold climates. Grow it in full sun in a gritty, sharply draining mix or lean garden soil; good drainage matters far more than winter cold, as wet, stagnant conditions in the cold season are the main cause of loss. Once established it is drought-tolerant, but unlike a true desert plant it appreciates occasional water during active growth and dry spells.
In the ground it makes a superb groundcover for rock gardens, walls, gravel beds and between paving, quickly knitting into a low mat. In containers, use a free-draining medium and avoid letting the pot sit waterlogged. Keep plants on the dry side through winter and see Watering and Repotting for general technique. Because it is so hardy, it can be overwintered outdoors across a wide range of climates where most succulents would perish.
Propagation
Propagation is very easy. The trailing stems root freely where they touch the soil, so established mats can simply be lifted and divided, or rooted pieces detached and replanted. Stem cuttings taken during the growing season root quickly in a gritty, barely moist medium. The species can also be raised from seed, though vegetative methods are faster and keep the plant true. See Propagation — offsets for related techniques with mat-forming succulents.
Common problems
- Rot — the usual killer, caused by poor drainage or wet feet during cold, dormant periods rather than by cold itself; sharp drainage is essential.
- Thin or leggy growth — too little light produces sparse, stretched stems and few flowers; give it as much sun as possible.
- Pests — generally trouble-free outdoors, but mealybugs and aphids can appear on stressed or sheltered plants (see Pests and diseases).
See also
- Delosperma — the genus overview
- Soil and potting mix · Watering · Propagation — cuttings · Propagation — seed · Repotting