Aulax umbellata is a slender shrub, up to 2.5 metres tall, with bright yellow flowers contrasting vividly with the purplish brown young foliage around the flowers during summer (from November to February).

Aulax umbellata is one of the three species which form the genus Aulax, the other two being Aulax cancellata, the channel-leaf featherbush and Aulax pallasia, the needle-leaf featherbush. The genus name is from the Greek aulax, a furrow. This refers to the channelled leaves of Aulax cancellata. The species name umbellata refers to the umbel shaped, nearly flat female flowerheads.The plants of the genus Aulax are dioecious, with separate male and female plants. The flowers of the male plants are bright lemon yellow, arranged in small lax spikes, which open over a period of several weeks. The new leaves of some of the plants are a beautiful purplish brown from early September, slowly fading to green after the end of the flowering period. The leaves of Aulax umbellata are more or less needle shaped, but considerably wider than the other two species, and this is the main distinguishing characteristic for the species.

The images below are of a narrow leafed form collected near Kleinmond.

Aulax umbellata is part of an ancient plant family, the Proteaceae, which had already divided into two subfamilies, the Proteoideae and the Grevilleoideae, before the break-up of the Gondwanaland continent about 140 million years ago. Both these subfamilies occur mainly in the Southern Hemisphere. In southern Africa there are about 360 species, of which more than 330 species are confined to the Cape Floral Kingdom, a relatively tiny portion of South Africa between Nieuwoudtville in the northwest and Grahamstown in the east. The extreme diversity of growth habits, flower forms and colours prompted the botanist Linnaeus to name this family after the Greek god Proteus, who could change his shape at will. Other well-known genera of the Proteaceae are Leucospermum with brightly coloured pincushion flowers, Protea with some of the most spectacular flowers imaginable, Leucadendron with decorative woody cones and Serruria, of which Serruria florida, the blushing bride, with its beautful pale pink flowers is the most well-known.

Aulax umbellata occurs mainly on coastal lowlands in the Western Cape province, from Kogelberg to Stilbaai, where it often forms dense stands. The plants grow in very well drained sandy soil.

The pollen of Aulax umbellata is not wind dispersed and although there is no nectar in the female flowers, the pollination is done by insects. The resulting fruits are small nuts, usually covered with long white hairs, only a few of the fruits in the female flowerheads are viable. The seeds are kept for up to six years in the flowerheads, but two year old seed shows the highest germination percentage, this declines the older the seed becomes.

Growing Aulax umbellata

Aulax umbellata is sown from the middle of March, when the day temperature starts to drop. The difference between the day- and night temperatures should be about 15ºC, the night temperature being the most important, preferably not above 10ºC. The seed is sown in open seedbeds, in a light, well drained soil and covered with a layer of sand (about 1 cm or 1½ times the size of the seed). The bed is then covered with a grid to protect it against attacks from birds and rodents. The seed will germinate three to four weeks after sowing.

Aulax umbellata prefers to grow in a well drained sandy soil with a layer of mulch of about 3 cm thick around the plants to keep the soil moist and the roots cool. The root system is very sensitive and should not be disturbed by loosening the soil once the plant has settled and is growing. Like all Proteaceae, it needs full sun and free air circulation. Plants generally take three or four years to flower from seed.

Aulax umbellata shrubs are quite hardy and do not suffer much from pests. The most harmful and destructive diseases are fungal. Most losses occur during the summer months when a virulent root fungus (Phytophthora camphora) can attack the plants. Control through the use of fungicides in the garden is difficult and expensive. By the time the plant shows distress, it is normally too late to arrest the problem. The best methods of control are cultural, i.e. water plants early in the morning; keep soil surface cool by mulching; remove diseased plants immediately; do not over-water in summer and prune and remove diseased material.

Aulax umbellata occurs in fire prone vegetation, where natural fires occur every ten to thirty years. This 'Mediterranean' type of vegetation grows in soils with very low amounts of nutrients. These nutrients are used up by the plants during their lifetime and need to be returned to the soil to provide the food for a new generation of plants. Natural fires occur mainly in late summer or autumn and are followed by the first winter rains, which provide the moisture the young seedlings need to grow to a size at which they can survive the long, hot summer. The fire itself, as well as the smoke it produces, is thought to play a role in damaging the thick seed coat of the small nuts and stimulating the germination process.

References:

• The inflorescence morphology and systematics of Aulax (Proteaceae) by J.P. Rourke, S. Afr. J. Bot., 1987, 53(6).
• South Africa's Proteaceae by Marie Vogts.
• Sasol Proteas, a field guide to the Proteas of Southern Africa by Tony Rebelo.
• The Protea Growers Handbook by Lewis Matthews.
• Grow South African Plants, compiled by Fiona Powrie.

H.G. Jamieson.
Kirstenbosch National Botanic Garden,
November 2001