Hypocalymma is a small genus of about 29 species, all of which occur naturally only in south Western Australia. H.angustifolium and H.cordifolium are the best known members of the genus and are widely cultivated. H.xanthopetalum is also becoming reasonably well known and seems to be adapting well to cultivation. It is a small, spreading shrub from 0.5 to 1.5 metres high with small, oval-shaped leaves about 10 mm long. In late winter and spring the bright yellow flowers appear along the stems with 2 flowers together at each leaf axil. The flowers are about 10-12 mm in diameter.
This species is a very attractive garden plant and has been in limited cultivation for many years. It seems to becoming more readily available and is suitable for a range of climates including humid, east-coastal areas where other species from the south west are often difficult to maintain. The plant requires well drained conditions in full sun or dappled shade and it is tolerant of at least moderate frost. Annual pruning will help maintain a dense, bushy growth habit. It is a good species for use as cut flowers.
Propagation can be carried out from seed and, based on experience with the related H.angustifolium, improved germination may be achieved using smoked water. Propagation from cuttings is the preferred method and cuttings strike readily from hardened, current season’s growth.
Photo: Chris Clarke