Scantily known in cultivation, the starry pink-and-white flowers of this easily grown cormous plant really deserve a place in containers, shallow garden ponds and rock garden pockets.
Wurmbea stricta is a deciduous, winter-growing geophyte reaching up to 0.6 m high. The subterranean storage organ is a deep-seated, irregularly shaped corm surrounded by dark brown membranous outer tunics, and produces three narrow, very straight, erect or suberect, dark green leaves that resemble knitting needles. Its striking star-shaped flowers are produced alternately along an elongated spike, the tepals varying in colour from pure white to pale pink. Each tepal has a small claw at the base and two prominent, deep pink glands that produce nectar. Vast quantities of seed are produced in attractive erect, narrowly egg-shaped capsules.
Wurmbea stricta, together with Wurmbea punctata, differ from most other wurmbea species by having their petals completely separate rather than being joined at the base into a short or long tube. Wurmbea punctata is a smaller plant with white to ddep pink pink flowers and lance-shaped leaves, occurring on stony hillsides and seeps in the Western Cape.
Distribution and habitat
Wurmbea stricta is a common species in seasonally inundated swamps and pools, and in roadside ditches, occurring in heavy clay soil. It grows in full sun and is found throughout the southwestern, western and northern parts of the Western Cape, and in southern Namaqualand. It likes company and forms large colonies, often flowering en masse. The flower spikes appear from late winter to late spring, blooming for a period of two to three weeks.
Derivation of name and historical background
Until recently Wurmbea stricta was included in the genus Onixotis and before then was known as Dipidax triquetra. Recent molecular studies have led to the genus Onixotis being combined with Wurmbea. The genus Wurmbea is named after F. von Wurmb, a Dutch merchant in Java. The specific epithet stricta is derived from the Latin, meaning very straight, and refers to the straight leaves that resemble knitting needles.
Honey bees pollinate the flowers of Wurmbea stricta.
Growing Wurmbea stricta
Wurmbea stricta is easily maintained under cultivation provided a few simple points are borne in mind. The plants are deciduous and winter-growing, and are completely dormant during the summer months. The corms are planted in early autumn, such that they rest 3-4 cm below soil level. They are well suited to deep containers, rock garden pockets and herbaceous borders, and must have very bright light, or preferably full sun for at least half the day, in order to flower successfully. Potted specimens can also be submerged into shallow garden ponds, allowing about 5 cm of water above the rim of the pot, and removed and dried off completely in early summer. The flowers remain open even in cloudy weather, individual blooms lasting five to six days.
The plants perform equally well in boggy and well-drained conditions, but must be dried off completely during the summer dormant period, otherwise the corms tend to rot. The corms should be stored in dry soil in summer to prevent shrivelling. Wurmbea stricta is cold tender, requiring the protection of the cool greenhouse or conservatory in cold climates. The flowers are displayed to great advantage when interplanted with low-growing, late winter- and spring-flowering buchu species, such as Agathosma glabrata and Acmadenia heterophylla. The seed capsules of W.stricta develop rapidly and are attractive when ripe, displaying their dark brown, irregularly shaped seeds.
The plants are easily propagated by corm offsets that develop towards the end of the winter growing period. They can be separated from the adult corms at any time during the summer dormant stage by gentle tugging, and be replanted in autumn. Seeds are sown in mid-autumn, once night temperatures have cooled down significantly. The seedlings are most successfully raised in a well-drained medium such as equal parts of river sand and finely sifted compost, in deep seed trays or raised beds, placed in bright light or full sun, and watered every two to three days using a watering can with a fine rose cap. Seedlings should remain undisturbed for two years, and then be lifted and planted into containers or out into the garden in early autumn, at the beginning of their third growing season, during which they should flower for the first time.
Wurmbea stricta is not particularly susceptible to pests or diseases, but the petals are sometimes nibbled by snout weevils, and the corms may become infested with mealy bugs when grown in containers. Fungal rotting of the corms may occur if they are not dried off sufficiently over the summer months.
References and further reading
- Duncan, G.D. 2000. Grow bulbs. Kirstenbosch Gardening Series. National Botanical Institute, Cape Town.
- Du Plessis, N.M. & Duncan, G.D. 1989. Bulbous plants of southern Africa. Tafelberg, Cape Town.
- Jeppe, B.J. & Duncan, G.D. 1989. Spring and winter flowering bulbs of the Cape. Oxford University Press, Cape Town.
- Vinnersten, A. & Manning, J. 2007. A new classification of Colchicaceae. Taxon 56(1)
Kirstenbosch National Botanical Garden
(Name updated 2008)