Leucadendron laxum I.WilliamsFamily: Proteaceae. |
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Leucadendron laxum is a decorative member of the protea family. This much-branched, dense shrub has a single stem at ground level, with short branches clustered at the base of the plant. It is evergreen, with small needle-like leaves and grows to between 1,5 and 1,75 m high in cultivation. It is dioecious (i.e. unisexual with male and female flowers on different plants), and both male and female plants produce masses of small bright yellow flowers during spring and early summer (September to October). On the female plants the flower-heads develop into very attractive small rosy-pink cones resembling opening rosebuds, remaining decorative until the seeds ripen during autumn (March) the following year. The cones can be dried and used in dried flower arrangements or in Christmas wreaths.
Leucadendron laxum occurs in dense stands near the most southern point of the African continent, where the Atlantic and Indian Oceans meet, where it grows on the level, damp ground in the valleys between Hermanus, Bredasdorp and Agulhas. How much longer the plants will be seen growing in the wild is not certain, as its habitat is being drained and farmed. As a result its status in the Red Data Book is: endangered. Leucadendron laxum is pollinated by insects, which are attracted by the slight, faintly unpleasant smell of the flowers. The fruits on the female plants ripen about six months later and appear as small, slightly mottled nutlets. These fall on the ground as the cones dry out and open up. It is very unusual to find young seedlings in between the mature plants and regeneration normally only takes place after a fire. Leucadendron laxum 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. 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 fire itself, as well as the smoke it produces, is thought to play a role in damaging the thick seed coat of the small nuts and stimulate the germination process. Leucadendron laxum is part of an ancient plant family, the Proteaceae, which had already divided into two subfamilies, the Proteoideae and the Grevilleoideae, before the break-up of the Gondwanaland continent about 140 million years ago. Both these subfamilies occur mainly in the Southern Hemisphere. In southern Africa there are about 360 species, of which more than 330 species are confined to the Cape Floral Kingdom, a relatively tiny portion of South Africa between Nieuwoudtville in the northwest and Grahamstown in the east. The extreme diversity of growth habits, flower forms and colours prompted the botanist Linnaeus to name this family after the Greek god Proteus, who could change his shape at will. More than 93 species, subspecies and varieties, all of them woody shrubs, belong to the genus Leucadendron. Other well-known genera of the Proteaceae are Leucospermum with brightly coloured pincushion flowers, Protea with some of the most spectacular flowers imaginable and Serruria, of which the Serruria florida, the blushing bride, with its pale pink flowers is widely used in bridal bouquets. The genus name Leucadendron is from the Greek leukos, white and dendron, tree, referring to the silver tree, Leucadendron argenteum, on which this genus was based. The species name laxum refers to the growth habit of Leucadendron laxum. The Afrikaans common name vleirosie is very descriptive, as it refers both to the habitat (a 'vlei' is a wet low-lying area) and the most attractive aspect of the plant ('rosie' for rose-bud like female cone). Growing Leucadendron laxum Leucadendron laxum is a worthwhile addition to the garden, where it is shown to best advantage in dense plantings in a sunny spot, where it will provide pleasure with its bright yellow flowers and attractive cones. Its flowers, cones and foliage make it a useful addition to flower arrangements. Leucadendron laxum prefers to be planted in a damp situation or needs to be watered regularly. Like all Proteaceae, it needs full sun and good air circulation. Leucadendron laxum shrubs are quite hardy and do not suffer much from pests. 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. Propagation of Leucadendron laxum is by seed sown from the middle of March (autumn), when the temperatures start to drop. It appears to be the difference between the day- and night temperatures that triggers germination. This temperature difference should be about 15ºC, but it is the night temperature that is the most important. It is only after the night temperature drops to 10ºC or lower that germination occurs. The seed is sown in open seedbeds, in a light, well drained soil and covered with a layer of sand (about 1 cm or 1½ times the size of the seed). The bed is then covered with a grid to protect it against attack from birds and rodents. The seed will germinate three to four weeks after sowing and the plants generally flower in their third or fourth year. References:
H.G. Jamieson.
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