Learn more about gardening with Delosperma:
The Tales & The Botany: Delosperma nubigenum
Delosperma nubigenum from Lesotho, grows at altitudes above three thousand meters and can survive frost and snow, inspiring breeding programs that produced the cold-hardy “Jewel of Desert” hybrids now common in temperate gardens.
The name Delosperma, meaning “visible seed” in Greek, refers to the transparent membranes of its fruit capsules through which the seeds can be seen.
Early European botanists were fascinated by the plants’ glistening leaves, believing that the crystals might be salt or even frozen dew, hence the enduring common name “ice plant.”
Modern botanists, however, value Delosperma for different reasons: the mechanical elegance of its seed capsules, which move with changes in humidity without any living tissue, offering insights into natural materials engineering.
Delosperma is a genus of succulent perennials belonging to the Aizoaceae, the ice plant family.
Native to southern and eastern Africa, these plants thrive in arid and semi-arid landscapes, from the rocky slopes of South Africa’s Cape provinces to the high mountains of Lesotho and Ethiopia.
They form low, spreading mats or cushions, rooting along the stems as they creep across the ground.
The leaves are opposite, fleshy, and usually cylindrical or triangular in cross-section.
Under sunlight their surfaces glisten because of epidermal bladder cells filled with water; these translucent cells scatter light and give the plants their characteristic icy sparkle while serving as miniature reservoirs that reduce water loss and leaf temperature.
I've taken some nice photos of Delosperma cooperi where you can really see the bladder cells twinkle and sparkle: check it out here!
Floral Morphology
The flowers of Delosperma are solitary or borne near the tips of the shoots.
They open only in bright sunlight and close at night or on dull days.
Each bloom is radially symmetrical, composed of a small calyx of five sepals surrounding a radiant halo of petaloid staminodes.
These colorful, strap-shaped filaments—often magenta, violet, orange, yellow, or white—are modified sterile stamens rather than true petals > an optimization in and of itself one might add.
Delosperma nubigenum has bright yellow flowers.
At the center stands a tuft of fertile stamens encircling the inferior ovary.
When pollination succeeds, the ovary develops into a dry capsule that demonstrates one of the genus’s most remarkable traits: hygrochasy.
What is hygrochasy?
The opening of a fruit (or flower) in reaction to the presence of rain.
This means that the capsule carrying the seeds ONLY opens when it is moistened by the rain - closing again as it dries.
This mechanism ensures that seeds are dispersed precisely when conditions favor germination.
In-sane.
Ecology
Pollination is usually carried out by bees, flies, and butterflies attracted by the brilliant colors and reflective sheen of the flowers rather than by fragrance.
In their native habitats, Delospermas occupy niches between rocks and in thin soils where water drains rapidly.
Their compact roots and succulent leaves make them perfectly suited to such conditions, and these same adaptations have made them popular garden plants in regions with hot summers and cold winters.
