Delosperma basuticum

Possibly the hardiest species of Ice Plant, this is native to the Drakensburg Mountains of South Africa. It forms a low cushion of rubbery, succulent green leaves. Good-sized starry yellow flowers have a white centre, the blooms resting right on top of the leaves in summer. Requires excellent drainage in winter, best grown in a gravel scree or alpine trough. Very drought tolerant once established. Flowers are attractive to butterflies. Evergreen. Could well prove to be hardy in Zone 4 or colder, provided with good drainage and reliable snow cover. Has potential as a green roof plant. Also suitable for growing between flagstones in a patio or path.