Thanks again to UBC horticulturist Jackie Chambers for contributing a couple photographs and a write-up!
Dicoma capensis is a prostrate perennial, found hugging the dry, sandy soils of Namaqualand and other arid areas of South Africa and Namibia. The stems of individual plants can reach 30cm in length. These stems scramble across the ground, forming small mats of narrow, grey-green leaves covered with dense white hairs. These mats can be seen from quite a distance shimmering in the African sun, and they draw you in for a closer look.
Closer inspection reveals purple flower heads, 2-3cm in diameter, held at the tips of the slivery-leaved shoots. The flowers are produced in the spring – September and October in the southern hemisphere. The flower heads are composed of two types of florets. The outer florets are sterile, while the inner florets (with the pale purple petals) contain the reproductive structures. Two distinct types of florets are typical features of the Asteraceae (a basic diagram of Asteraceae flower structure).
While the purple flower heads are showy, they are upstaged by the amazingly spiky involucral bracts (the bracts at the base of the flower head, sometimes called phyllaries). Aluka has a technical description of Dicoma capensis flower structure.
The genus name Dicoma was derived from the Greek, di meaning “two”, and kome, meaning tuft of hair, a reference to the pappus bristles in the flower. Pappi are structures found at the base of individual florets in the Asteraceae flower head (see link above with image). The species name capensis is a reference to this species’ distribution around the Cape of Good Hope, and other areas of southern Africa.
Dicoma capensis is used in traditional herbal medicine of the Khoisan people of southern Africa. Not surprisingly, the plant was also incorporated into Cape Dutch medicine or boererate (farm remedies). One of its common names in Afrikaans is koorsbossie which translates as “fever bush”. Current research is investigating the active constituents of this species and its possible uses for treating a variety of conditions including cancer and AIDS.
There are several species of Dicoma found in southern Africa, including Dicoma anomala.