Delosperma congestum is a cold hardy succulent that makes spectacular flowers that glisten in the sun. It is an alpine plant that originates from the mountains of South Africa.
The common name for Delosperma is hardy ice plant, and this species is known as the congested ice plant. The name ice plant may be due to fact that the leaves are covered with papillose tissue which reflects light, giving the leaves a frost-covered look.
This plant is rated for zone 5 and is commonly found in nurseries in S. Ontario. Unfortunately, it is not a reliably hardy plant here. In drier zone 5 areas, such as the mid-western US, this is a reliable perennial but in the wetter eastern regions of North America, it seems to die out in winter, even when grown in a fast-draining, sandy substrate.
I have had very little luck overwintering this plant in the garden, but it is easy to grow in pots and overwinter in a cold fruit cellar. In fall, reduce watering and allow it to dry out. A light frost will not harm the plant. Before the real cold weather sets in, take the pot into the basement and store it cold. Water it once a month or so. Even in complete darkness, Delosperma will remain green. In spring bring it outside and condition it for full light.
A cultivar, named ‘Gold Nugget’ or ‘Golden Nugget’, exists and I suspect most plants in gardens are this cultivar. There is also a ‘White Nugget’ with white flowers, but it is a cultivar of D. basuticum. I have also seen a listing for D. congestum ‘Alba’.
Life Cycle: perennial
Height: 8cm (3in)
Bloom Time: summer
Natural Range: South Africa
Habitat: dry alpine regions
Cultivation of Delosperma congestum:
Light: full sun
Soil: well draining
Water: drought tolerant
USDA Hardiness Zone: (4?)(5?) 6- 9
Propagation: seed, division