Aulax umbellata
Introduction
A slender shrub with bright yellow flowerheads contrasting vividly with the purplish brown young foliage around the flowerheads during summer.
Description
Description
Aulax umbellata is a shrub with long slender ascending branches up to 2.5 metres tall, from a single main stem. The leaves are flat, linear to spathulate, but considerably wider than the other two species, and this is the main distinguishing characteristic for the species.
The plants of the genus Aulax are dioecious, with separate male and female plants. The flowers of the male plants are bright lemon yellow, in spike-like racemes in clusters at the ends of branches.
The male flowers have four perianth lobes, united into a tube at the base, slender anthers and thread-like style tipped with a club-shaped stigma that functions as a pollen presenter.
The female inflorescence is inside a cup-like structure made up of modified branchlets. Inside this cup the small cream flowers are arranged spirally on a conical structure in the centre.
These flowerheads are also clustered at the branch tips. The flowers open over a period of several weeks during summer (from November to February). Both male and female flowers lack floral nectaries.
The fruit is a small ovoid nut, densely covered with long white hairs. Only a few of the fruits in the female flowerhead 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.
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.
Conservation Status
Status
According to the Red List of South African plants, Aulax umbellata is assessed as Near Threatened (NT). Its wild population is estimated to have declined by 30% over the past 40 years because its range has been reduced by invasive alien plants, afforestation, farming and urban expansion. Its population is likely to decrease further in the future.
Distribution and habitat
Distribution description
Aulax umbellata occurs mainly on lower slopes and flats of the coastal lowlands in the Western Cape province, from the Kogelberg to Stilbaai, where it often forms dense stands. The plants grow in very well drained, sandy, acidic soil.
Plants in the western part of its range have needle-like leaves similar to those of Aulax cancellata but they lack the channel.
Derivation of name and historical aspects
History
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.
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.
Ecology
Ecology
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.
Aulax umbellata occurs in fire prone vegetation, where natural fires occur every ten to thirty years. This 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, plays a role in stimulating the germination process, and germination can be enhanced in the nursery by exposing the seeds to smoke.
Uses
Use
Aulax umbellata is an attractive garden plant, best suited to fynbos gardens. The female flowerheads when dried make woody stars that make interesting decorations.
Growing Aulax umbellata
Grow
Aulax umbellata seed is sown in autumn, 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.
References
- Matthews, L. 1993. The Protea Growers Handbook. Trade Winds Press, Durban.
- Powrie, F. 1998. Grow South African Plants. A gardener's companion to indigenous plants. National Botanical Institute, Cape Town.
- Rebelo, A.G. 2001. Proteas. A field guide to the proteas of southern Africa, edn 2. Fernwood Press, Vlaeberg, Cape Town.
- Rebelo, A.G. et al. 2006. Aulax umbellata (Thunb.) R.Br. National Assessment: Red List of South African Plants version 2017.1. Accessed on 2017/05/03
- Rourke, J.P. 1987. The inflorescence morphology and systematics of Aulax (Proteaceae). S. Afr. J. Bot., 53(6): 464-480.
- Vogts, M. 1982. South African's Proteaceae: know them and grow them. Struik, Cape Town.
Credits
H.G. Jamieson
Kirstenbosch National Botanic Garden
November 2001
Updated by Alice Notten
Kirstenbosch National Botanical Garden
May 2017
Plant Attributes:
Plant Type: Shrub
SA Distribution: Western Cape
Soil type: Sandy, Loam
Flowering season: Early Summer, Late Summer
PH: Acid, Neutral
Flower colour: Cream, Yellow
Aspect: Full Sun
Gardening skill: Average
Special Features:
Good potplant
Hedge/screen
Horticultural zones
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