Lapeirousia corymbosa

(L.) Ker Gawl.

Family : Iridaceae
Common names
:blue cabong (Eng.); bloucabong, koringblom, koringblommetjie (Afr.)

Corymb of flowers

Lapeirousia corymbosa is a cheerful bulbous plant with striking blue to purple blooms that does wonderfully when planted in containers on a sunny patio and helps attract an interesting array of nectar-feeding pollinators such as butterflies and moths to your garden.

Description
Lapeirousia corymbosa is a perennial, cormous geophyte (a plant that propagates from an underground tuberous, bulb-like rootstock) that grows to a height of 50–150 mm. The stems are flattened and have distinct, leaf-like bracts with crisped margins. The leaves (mostly one, sometimes two) are basal, curve to form a sickle shape and have wavy margins and a distinct midrib.

PLant showing sickle shaped leaves

The flowers are pale to deep blue with a white central star and are borne on a much-branched stalk in a flat-topped cluster (or a ‘corymb'- hence the name). Flowering occurs mainly from September to November.

Conservation status
Expanding agriculture and urban development have caused a 30% loss in habitat for this species and therefore it has been listed as ‘Declining' on the Red List.

Distribution and habitat
Lapeirousia corymbosa occurs on sandy and granitic slopes in the southwestern Western Cape from Piketberg to Agulhas.

Derivation of name and historical aspects
The genus ‘ Lapeirousia ' is named after the French botanist Baron Phillippe Picot de la Peyrouse (1744–1818), and ‘ corymbosa ' comes from the word corymb which means a flat-topped cluster of flowers in which the outer flower stalks are longer than the inner ones. The common names ‘ cabong ' and ‘ chabi ' are the names given by the Khoisan hunter-gatherers for several species of Lapeirousia. The genus is endemic to sub-Saharan Africa and comprises 41 species.

Ecology
The genus Lapeirousia is well known for its species with long floral tubes (20–70 mm) and bright magenta to deep purple flowers which are pollinated by long-tongued flies and tangle-wing flies. These flies have slender, siphon-like mouthparts long enough to reach the nectar at the bottom of the long floral tubes of species such as L. oreogena and L. anceps . L. corymbosa, however, has a short floral tube (4–7 mm) and is considered to be a generalist species, pollinated by a diversity of nectar-feeding insects such as butterflies, moths, bees and bombyliid flies . Many closely related species of Lapeirousia have adapted to grow on very different, yet adjacent soil types, and this is believed to be the main driving force behind their speciation.

Like most Cape bulbs, these plants are dormant in the dry hot summer months.

Uses and cultural aspects
The very first ethnobotanical survey to be completed in South Africa was done by Simon van der Stel in Namaqualand, where many Lapeirousia species occur. In his survey he recorded that the Khoisan hunter-gatherers used the underground stems (corms) of many Lapeirousia species as an important daily food source, roasting them in hot ash. The taste of the roasted corms is reported to be sweet, yet slightly astringent.

Brilliant blue flowers

Growing Lapeirousia corymbosa

Lapeirousia species grow well in full sun and are best maintained in deep containers where they can enjoy a sunny spot for as much of the day as possible. Plant the corms in autumn, about 20 mm deep, in a well-draining, sandy medium with 50 mm of finely sifted compost at the bottom of the container. Give the plants a thorough watering once or twice a week during spring and the winter growing season, but during the summer dormant period the plants should remain completely dry.Corms are known to go dormant for one or more growing seasons despite sufficient moisture and therefore rarely produce offsets for propagation.

Sow seeds of Lapeirousia corymbosa in autumn. The very hard seeds have a long dormancy period, and therefore a low percentage of fresh seeds germinate in the first winter season, but germination improves by the second year and is usually most rewarding in the third. Once germinated the seedlings grow fast and flower usually in the second or third year. There are no serious pests or diseases associated with Lapeirousia corymbosa , but check regularly for any aphids on the flowers and treat with soapy water or an aphicide.

References and further reading

  • Duncan, G.D. 2010. Grow bulbs. Kirstenbosch Gardening Series. South African National Biodiversity Institute, Cape Town.
  • Du Plessis, N. & Duncan, G. Bulbous plants of southern Africa: a guide to cultivation and propagation. Tafelberg, Cape Town.
  • Goldblatt, P. & Manning, J.C. 1992. Systematics of the Southern African Lapeirousia corymbosa complex (Iridaceae- Ixioideae), with L. neglecta sp. nov. South African Journal of Botany 58 (5): 326–336.
  • Goldblatt, P. & Manning, J.C. 2000. Iridaceae. In O.A. Leistner (ed.), Seed plants of southern Africa. Strelitzia 10: 623–638. National Botanical Institute, Pretoria.
  • Jeppe, B.J. & Duncan,G.D. 1989. Spring- and winter-flowering bulbs of the Cap e. Oxford University Press, Cape Town.
  • Manning, J. & Goldblatt, P. 2000. Cape plants. A conspectus of the Cape flora of South Africa. Strelitzia 9. National Botanical Institute, Pretoria.
  • Manning, J. & Paterson-Jones, C. 2004. Southern African wild flowers: jewels of the veld. Struik, Cape Town.
  • Manning, J.C. 2007. Field guide to fynbos . Struik, Cape Town.
  • Stearn, W.T. 1992. Stearn's dictionary of plant names for gardeners . Timber Press, Oregon.
  • Website: Red List of South African Plants , http://redlist.sanbi.org/index.php .

 

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This page forms part of the South African National Biodiversity Institute's plant information website www.plantzafrica.com.


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