Silver Tree, Silver Leaf Tree
Silver trees are wonderful garden ornamentals. Leucadendron Argenteum, the shimmering Silver Tree, is one of South Africa’s iconic trees. It was first mentioned in a manuscript of the early 17th century when dense stands of it covered large areas of the Cape Peninsula.
With urbanisation, forestry and agriculture, it is now limited to isolated patches on Lion’s Head and the lower eastern slopes of Table Mountain around Rhodes Memorial, at Kirstenbosch and on Wynberg Hill, and there are several populations in the mountains at Paarl, Stellenbosch and Somerset West which are said to have been planted.
In centuries past it was widely planted for firewood, but is now grown exclusively as a garden ornamental. Leucadendron Argenteum is one of several members of the Proteaceae family with silvery leaves. The shimmering, silvery effect is most noticeable in summer and arises from the light reflected off the dense covering of fine silky hairs which lie flat against the surface in hot weather, but stand erect on cool days, giving it a greener appearance.
The Silver Tree, like all other members of the genus Leucadendron, is dioecious, meaning that the flower heads consist either of male or female flowers, and are borne on different plants. The male flower heads are relatively soft balls of light pink and yellow whereas the female flowers are produced between silvery bracts which develop into hard cones. The leaves surrounding the flower heads of the male trees are prominent and become very shiny, sometimes turning yellow on the inner surfaces, whereas the cones of the female flower heads remain enclosed within the leaves.
Silver trees are adapted to fire cycles in the wild and survive by means of re-seeding. The trees are usually killed by summer fires but the seeds within the female cones survive and are stimulated to germinate within a few weeks of autumn rains. Silver Trees are fast-growing, upright trees reaching 8-10 m high, with a spread of 2-3 m. In the garden, the silvery effect provides excellent contrast against the light to dark green shades of surrounding garden shrubs and trees. Flowering takes place from late August to October.
Silver Trees make excellent specimen trees for small to medium-sized gardens and are ideal for group plantings in large fynbos gardens. They grow very well in acid, granitic soils but easily adapt to well drained, acid, sandy soils. Incorporate well rotted compost into the planting hole but do not use manure or chemical fertilisers as these will burn the roots.
Young trees require regular deep watering in winter for their first two years, but once established they are water-wise. They need full sun and free air circulation. Established trees can take occasional light frost. Care must be taken not to disturb the roots as this makes them susceptible to the root-rot fungus Phytophthora cinnamomi.
Silver trees generally live for only about 20 years, so it is wise to plant replacement trees at staggered intervals. Plant Silver Trees from nursery bags in late autumn, once temperatures have cooled down considerably, or alternatively, sow fresh seeds in autumn in seedbeds in an acid, well-drained sandy medium. Pot-up seedlings individually into bags once their first two true leaves appear and plant out into the garden the following autumn. Dried Leucadendron Argenteum silver leaf branches and the dried female cones make wonderful Christmas decorations.