Leucadendron macowanii E.Phillips

Family: Proteaceae
Common name: Acacia-leaf conebush

Leucadendron macowanii

This is a fast-growing shrub with narrow, dark green leaves, bright yellow flowers in profusion on the male plants in spring, and reddish brown cones on the female plants in late summer. It is an excellent plant for landscaping and looks best when planted in small groups of five to seven plants.

Conservation status: Endangered

Male flower headsLeucadendron macowanii was named after one of the first professors of botany in Cape Town, Professor Peter MacOwan, who collected a specimen in the Wynberg area in the southwestern Cape around 1883. This is now a very rare species, due to displacement by agriculture and urban development. It has completely disappeared from the Wynberg area and only occurs in a valley near the Cape Point Nature Reserve, where the only remaining population is being threatened by the invasion of the area by alien Acacia species. These alien trees not only suppress the growth of the remaining plants, but the Acacia leaves are similar to those of Leucadendron macowanii and some plants have been mistakenly killed during clearing operations.

Female conesThe shrubs grow up to 2 m tall and have a single main stem. They are quite fast growing and should have attained a height of 2 m in three to four years from the date of sowing. The plants flower during July and August with bright yellow flowers, with the male plant looking the most attractive. The female flowers occurring in the immature cones are very small. When mature, the cones are about 30 mm long and reddish brown in colour. They are quite attractive on the plant as well as in flower arrangements. The seeds are retained in the cones till they are released by fire or by drying of the cones.

Leucadendron macowanii occurs in fire-prone vegetation, where natural fires occur every ten to thirty years. This 'Mediterranean' type of vegetation grows in soils with very low amounts of nutrients. These nutrients are used up by the plants during their lifetime and need to be returned to the soil to provide the food for a new generation of plants. Leucadendron macowanii is adapted to survive the fires by producing seeds throughout its lifetime, some of the seeds being distributed and stored in the soil, others being stored in the old cones, which will only be stimulated to open and release the seeds when the plant dies or is killed by fire. These natural fires occur mainly in late summer or autumn and are followed by the first winter rains, which provide the moisture the young seedlings need to grow to a size at which they can survive the long, hot summer.

The genus Leucadendron has the only 10 Proteaceae species in southern Africa which are exclusively wind-pollinated and Leucadendron macowanii is one of these. The wind-pollinated species have two main characteristics: they do not secrete nectar and they are odourless. The flowers of the female plants have large stigmas for filtering pollen out of the air. In the male plants, the pollen does not adhere to the pollen presenter, but when the flower opens it is scattered in large showers and drifts away in the wind (Rebelo 1995).

Growing Leucadendron macowanii

Leucadendron macowanii is an easy shrub to grow in a normal garden situation where regular watering occurs. In their original habitat the plants grow in damp sands near streams and when planted in gardens do need regular watering to grow to their full potential. The soil should be well drained and the plants should be in full sun. They are best planted in small groups of five or seven plants, about 1.5 m apart, so that both male and female plants can be expected to be present.

Although the plants can be propagated vegetatively by making cuttings, the propagation is best done by seed, sown from the middle of March (late summer), when the day temperature starts to drop. The seed is sown in open seedbeds, in a light, well-drained soil and covered with a layer of sand (about 1 cm or 1 1/2 times the size of the seed). The bed is then covered with a grid to protect it against attacks from birds and rodents. The seed will germinate three to four weeks after sowing.

The plants can be damaged by leaf borers, but generally look healthy and do not suffer from many disfiguring diseases. Like all other Proteaceae, the most harmful and destructive diseases are fungal. Most losses occur during the summer months when a virulent root fungus (Phytophthora camphora) can attack the plants. Control through the use of fungicides in the garden is difficult and expensive. By the time the plant shows distress, it is normally too late to arrest the problem. The best methods of control are cultural, i.e. water plants early in the morning; keep soil surface cool by mulching; remove diseased plants immediately; do not over-water in summer and prune and remove diseased material.

VOGTS, M. 1982. South Africa's Proteaceae: know them and grow them. Struik, Cape Town.
REBELO, A.G. (Tony). 1995. SASOL Proteas. A field guide to the proteas of southern Africa. Fernwood Press, Vlaeberg, Cape Town.
REBELO, A.G. (Tony). 2000. Proteas of the Cape Peninsula. National Botanical Institute, Claremont.
MATTHEWS, L. 1993. The Protea growers handbook. Trade Winds Press, Durban.

H.G. Jamieson.
Kirstenbosch Botanic Garden
September 2002

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