Chasmanthe bicolor is a highly ornamental garden subject, which stands out from the other two species in this genus. It is one of three species in the genus, the others being Chasmanthe floribunda, which has a yellow variety C. floribunda var. duckittii and Chasmanthe aethiopica.
This plant is a winter-growing, cormous geophyte up to 1.3 m high. The corm is 45mm in diameter, is slightly depressed and surrounded with several layers of dark brown, scaly leaf bases called tunics.
Although the flower is smaller that the other two species in the genus, it is more striking. The upper tepals of the flowers are orange-scarlet, whereas the bottom tepals are dark green with a yellow tube. The flowers are alternately arranged on both sides of the peduncle with as many as 28 blossoms. It blooms from midwinter to early spring (June-Sept.).
The leaves are sword-shaped and have a silky feel and look, with a prominent vein in the centre of each leaf. The leaves are arranged in a fan.
Vulnerable, meaning that it faces a high risk of extinction in the wild. Chasmanthe bicolor is known from only three sites, but since its habitat is not well explored, it is estimated that there are approximately ten locations where it grows. It is declining as a result of crop farming, construction of dams and because alien plants are invading its habitat.
Distribution and habitat
Chasmanthe bicolor is endemic to the Western Cape Province of South Africa. It occurs in sheltered ravines and in open woodland near streams in the Robertson district, between McGregor and Swellendam. Its full geographic range is, however, not well known.
Derivation of name and historical aspects
The name Chasmanthe means 'gaping mouth', from the Greek words, chasme, meaning gaping, and anthos, flower, referring to the shape of the flower. The word bicolor is Latin for two-coloured; referring to the colour of the flowers.
The brightly coloured flowers of Chasmanthe bicolor ensure that the pollinators, sunbirds, are attracted to the plants. The flower has a wide base which contains nectar. The beak of the Orange-breasted sunbird and the Malachite sunbird is perfectly shaped to fit the curves of the flower. When the bird inserts its beak into the flower in search of nectar, the pollen on the stamen is deposited onto its head.
Uses and cultural aspects
This plant can be used to bring much needed colour to those difficult semi-shaded areas in the garden. It can also be used as a container plant.
Growing Chasmanthe bicolor
Chasmanthe bicolor is very easily propagated. The pea-sized seeds are ready to be harvested once the capsule starts to split open. Sow in autumn (mid-April to May), 3-5 mm deep. This can be sown in deep seed trays, pots or seedbeds. Use a well-drained medium (1 part river sand or silica sand and 1 part fine compost). Fresh seed germinates within 3 to 4 weeks. Keep moist, water every 2 to 3 days with a fine sprayer. Large, mature clumps can be lifted and divided every 3 to 4 years. This must happen in the dormancy stage (during the summer and early autumn months).
References and further reading
- Goldblatt, P., Manning, J & Dunlop, G. 2004. Crocosmia and Chasmanthe. Royal Horticultural Society Plant Collectors Guide. Timber Press, Portland, Oregon
- De Vos, M P. 1985. Revision of the South African genus Chasmanthe (Iridaceae). South African Journal of Botany 51: 252-261
- Duncan, G. D.2001. Chasmanthe. Veld & Flora 87: 108-111.
- Goldblatt, P. & Manning, J. 2000. Cape Plants, A Conspectus of the Cape Flora of South Africa. Strelitzia 9. National Botanical Institute, Pretoria & Missouri Botanical Garden Press, Missouri.
- Raimondo, D., Von Staden, L., Victor, J.E., Helme, N.A., Turner, R.C., Kamundi, D.A. & Manyama, P.A. (eds) 2009. Red List of South African plants 2009. Strelitzia 25. South African National Biodiversity Institute, Pretoria.
Bernard Martin Brown
Kirstenbosch National Botanical Garden
(Updated by Alice Notten July 2011)