Antithrixia flavicoma is a beautiful but little-known shrub. With its large yellow flowerheads and silvery-grey leaves it is immediately noticeable in its natural habitat. However, it has only been collected in a few places in Namaqualand, indicating that it might be very restricted in distribution.
This plant is a woody shrub growing up to about 1 m high. It is moderately well-branched so it is often as broad as it is high. In flower, the shrubs are covered with lemon-yellow flowerheads, borne singly at the ends of the branches. The leaves are small, narrow and rounded, and are crowded into tufts arranged opposite each other on the stems. The branching pattern of the twigs is also opposite. A dense covering of white hairs on the upper leaf surface and on the young stems is responsible for the silvery-green appearance of the plant. The involucre (the lower part of the flowerhead that protects the seeds) is narrow, and consists of dry bracts (leaf-like structures which have taken on a different function than photosynthesis) which overlap each other like inverted roof-tiles. The base of each bract is greenish and tightly pressed against the flowerhead, while the tip is pale brown and curls away from the flowerhead. The flowers themselves are pale yellow and the reproductive parts (style, stigma and anthers) protrude above the flowerhead.
Note: in the daisy family or Asteraceae, what looks like a flower is actually an aggregation of very small flowers into a flowerhead. This flowerhead is similar to that found in the proteas, but in the daisies usually contains two kinds of flowers: small, tube-shaped disc flowers in the centre, and long strap-shaped ray flowers around the margin. Both of these kinds of flowers are present in Antithrixia flavicoma.
Antithrixia flowers in late spring (October to November). The seeds are dispersed by wind, and to enhance wind dispersal the seeds are equipped with a pappus of hair-like bristles.
Antithrixia could be confused with members of the genus Pteronia, which also have leaves arranged opposite each other on the stems, and occur in similar habitats. However, Pteronia flowerheads never have ray flowers.
This species is listed as VU (vulnerable) in the 2007 Interim Red Data List. This is probably due to its narrow distribution range, and it being known from only a few populations. The population featured in the photographs associated with this article, is protected in the Skilpad section of the Namaqua National Park. However, it appears to grow on a land-type that is often cultivated, which may result in great threat to populations outside of the National Park.
Distribution and habitat
Antithrixia flavicoma grows on soils associated with granite rocks in open places in the Kamiesberg region, although it has also been collected from near Sutherland on the Roggeveld escarpment. These regions have hot, dry summers and can get very cold in winter, regularly experiencing snow.
Derivation of name and historical aspects
The name is derived from the Greek-rooted anti- (meaning contrary to) and Athrixia (another southern African genus in the daisy family) and means ‘different from Athrixia '. There is only a single species of Antithrixia. It was described by De Candolle in 1838 from a collection at the Cape made by Drège. The closest relatives of Antithrixia are thought to be in the genera Relhania, Rosenia, Leysera and Oedera.
Ecology, uses and cultural aspects
There is almost no recorded information on the ecology of the species, its preferred habitat, biological interactions with other plants and with animals, or its uses or cultural aspects. Although it has not been recorded as a garden plant, it has horticultural potential as the shrubs flower profusely, the flowerheads are large and attractive and the foliage is very attractive in its own right.
Growing Antithrixia flavicoma
Unfortunately there are no records of this plant being cultivated, so there is no available information on how to grow it. However, many small, light, dry seeds are produced and seed is likely to be the best way to propagate the plant (A. le Roux, pers. comm.). It is likely to require rich, well-drained soil and full sun, and be tolerant of very cold conditions in winter.
References and further reading
- Anderberg, A. 1991. Taxonomy and phylogeny of tribe Gnaphalieae (Asteraceae). Opera Botanica 104: 1–195. Bremer, K. 1978. Oreoleysera and Antithrixia, new and old South African genera of the Compositae. Botaniska Notiser 131: 449–453.
- Harvey, W.H. & Sonder, O.W. 1894. Antithrixia. Flora capensis, vol. 3. Lovell Reeve & Co. Ltd., London.
- SANBI Threatened Plants Program Interim Red Data List. February 2009. http://www.sanbi.org/biodiversity/reddata.htm.
Compton Herbarium, Kirstenbosch Research Centre