Dimorphotheca cuneata (Thunb.) Less.
Common names: rain flower, white bietou, Karoo bietou (Eng.); reënblom, witbietou, karoobietou (Afr.)
Dimorphotheca cuneata is a hardy, mainly winter-rainfall perennial producing masses of showy, white flowers in early spring.
Dimorphotheca cuneata is an erect, hardy, bushy shrublet. The plant in its natural habitat may attain a height of 1 m. In cultivation it can grow as tall as 1.5 m. The leaves are linear, toothed, alternate and aromatic when crushed. The disc florets are yellow, the ray florets mainly a shasta white but their colour ranges from mostly white to orange and, in a few cases, pink. It has a semi-fibrous root system; the roots can go as deep as 1 m.
Dimorphotheca cuneata is perennial and plants can live up to 20 years in their natural habitat, in cultivation up to 15 years. It is drought-resistant and as such is ideal for water-wise gardens.
Dimorphotheca cuneata is not an endangered species.
Distribution and habitat
Dimorphotheca cuneata is widely distributed in arid and semi-arid regions of the Fynbos, Succulent Karoo, Nama Karoo and southern Grassland biomes. The geographic range of Dimorphotheca cuneata is from Touws River in the south to Springfontein in the southern Free State in the north. The species extends from Caltizdorp in the east to Springbok in the west.
The family Asteraceae (asters) is the largest plant family in southern Africa. Member species occur from elevations of 3000 m to sea-level. Asters occur in a variety of landscapes ranging from afromontane, karroid and arid to subtropical coastal belts and grasslands.
Derivation of name and historical aspects
The genus Dimorphotheca is derived from the Greek di = two and morphe= form; thus, dimorphotheca refers to the two distinct forms of fruit occurring in some species. The specific epithet cuneata means wedge-shaped.
Dimorphotheca cuneata flowers from September to late October. The flowers of this species open fully from 11:00 am, as do many other aster species. The reason for this is the need for sufficient sunlight and warmth.
Attracting the right pollinator is important in the floral biology of the species. Mainly bees and bumble bees pollinate the flowers during the day.
Dimorphotheca cuneata should be cultivated more in public and private gardens. It is cultivated at the Karoo Desert National Botanical Garden in Worcester and the Free State National Botanical Garden in Bloemfontein. Both these gardens have good displays in spring. The plants are known to produce prussic acid and as such are toxic to livestock, especially sheep.
Growing Dimorphotheca cuneata
Dimorphotheca cuneata occurs primarily in the winter-rainfall areas, but can be cultivated successfully in the summer-rainfall areas of South Africa.
Seeds germinate easily and mature one month after flowering. Seeds need to be gathered as soon as possible otherwise they will soon be lost to the elements, especially wind. Seeds are relatively large and flat, 10-12 mm in length and 8-10 mm in breadth. They are pale brown in colour. Sow the seeds in a seed pan during the cool autumn months (April to mid June in the southern hemisphere). Ensure that there is adequate drainage in the bottom of the seed pan. If the seeds stand in too much water they will more than likely rot. The best medium to sow the seeds in is a sandy loam mixture. On top of this mixture, sprinkle a thin layer of coarse river sand, 5 mm deep. It is into this sand that the seeds are sown. Keep the area weed-free and water every second day. During very hot and dry weather water daily, preferably in the early morning when it is cool. Ensure, when watering, that the seeds are not blasted out of the soil; gentle watering is advised. Ensure that the seed trays are positioned in a sunny area. Seeds should be sown 4 mm below the soil surface. If sown too deep, they will be smothered and probably not germinate. Plant the seedlings out in September/October of the same year when they are approximately 50 mm in height. Under ideal conditions seedlings will grow rapidly.
Plants can also be cultivated from cuttings. Soft tip growth must be used. Strike cuttings in a mixture of 50% perlite and 50% sharp river sand. Ensure that the cutting medium is kept moist. Feed with a foliar organic feed. Strike cuttings when the plant is actively growing. April, May or June are the preferred months for striking cuttings. The strike rate is medium to high (about 75%). Ensure that the cuttings are misted well.
Dimorphotheca cuneata flourishes in well-drained, sandy loam soils. They can be cultivated in pots or planted in groups in the garden. Remember to plant them in a sunny locality, otherwise they will not flower properly.
A word of warning: great care must be taken not to plant this species in heavy clay soils.
- Shearing, D. 1994. Karoo - South African Wild Flower Guide 6. Botanical Society of South Africa, Cape Town.
- Trinder-Smith, T.H. 2003. The Levyns guide to the plant genera of the southwestern Cape. Bolus Herbarium, University of Cape Town.
- Van Rooyen,G. & Steyn, H. 2004. Cederberg, Clanwilliam and Biedouw Valley. South African Wild Flower Guide 10. Botanical Society of South Africa, Cape Town.
Karoo Desert National Botanical Garden
Plant Type: Shrub
SA Distribution: Eastern Cape, Free State, North West, Northern Cape, Western Cape
Soil type: Sandy, Loam
Flowering season: Spring
PH: Acid, Neutral
Flower colour: White, Pink, Yellow, Orange
Aspect: Full Sun
Gardening skill: Easy