Tree usually up to 5m has a grey Bark. Simple Leaves have a hairy, glistening sheen. The dioecious flowers are in a compound inflorescence. Fruit is a heavy, woody cone with small, black nuts.
Leucadendron argenteum, Protea argentea.
Common names: Cape Silver Tree, Silwerboom, Silver Tree, Witteboom, Silver leaf tree.
Family: Proteaceae (Protea family). Name derivation: Protea – after the Greek sea god Proteus, who like the plants, had a variable appearance. Members of this family occur mainly in the southern hemisphere. Universal characteristics are few. All are woody trees or shrubs. Anthers are basifixed and the superior Ovary is sessile. Flowers are contained in a compound inflorescence and 4 Tepals are present. There are about 80 genera and at least 1 600 species including the Australian Macadamia. There are 16 genera and 300 species in the RSA. 6 genera have species that are trees. These are Brabejum, Faurea, Leucadendron, Leucospermum, Mimetes and Protea. Currently the genus Protea has the most species. Protea gaguedi is the only species found in Namibia. This family has similar to Leaves to the fossil Glossopteridales whose fossil leaf remains resemble the modern protea. These fossils were prevalent more than 200 million years ago. This was a time before the break up of Gondwanaland due to continental drift.
Name derivation: Protea – after the Greek sea god Proteus, who like these plants, had a variable appearance. argenteum – silvery referring to the leaves.
Conservation Status: Endangered. Assessment Date: 2009. Problems include exotic squirrels, invasive Alien Species – including plantations, and habitat loss due to agriculture and building, Fungi-like organisms in the genus Phytophthora are a problem worldwide and one species attacks the roots of the Leucadendron argenteum. This organism is different from “fungi” in that the cell wall is composed of cellulose whereas in the fungi cell walls contain chitin.
This giant protea is actually a small, evergreen, erect Tree may reach 5m high – occasionally reaching 15m. The thick, grey Bark has very distinctive horizontal leaf scars; otherwise, it is generally smooth and grey. Branches are upright.
The elliptic to narrowly obovate to lanceolate, usually spirally arranged Leaves are simple (have a single blade which may have incisions that are not deep enough to divide the leaf into leaflets). They tend to be concentrated at branch ends. They may reach 15 x 2cm and are usually wider than 1cm. Male plant leaves tend to be smaller. The leaves have an impressive Glistening Sheen. This is due to distinctively long, silky, silver hairs and is more prevalent when the hairs collapse against the surface to prevent water loss in summer. Male trees show this feature best. These hairs occur on both sides of the leaves. The leaf Base tapers and the Apex is narrowly tapering. Petioles (leaf stalks) are absent. The involucral leaves (one or more whorls of small leaves or bracts standing underneath a flower or flower-cluster) tend to hide the flower heads, which are usually higher up in the female flowers.
The dioecious (having male and female parts on separate plants), scented Flowers are contained in a compound inflorescence that develops at branch ends. The apricot coloured, shiny, solitary and inconspicuous Male Flowers are in short, compact capitula (globose or knoblike part, as in particular a dense flat cluster of small flowers or florets, as in the Asteraceae – daisy family) about 5cm long and slightly less wide. Small brown bracts are present. A circle of leaves surround these bracts. The woody, silvery, Female Flower heads may reach a length 10 x 6cm when mature and here, the semi-circular bracts are conspicuous. They are silvery with a pinkish tinge. Flowers are wind Pollinated. In both male and female flowers, the Perianth (the 2 floral envelopes considered together; a collective term for the calyx and corolla) is cylindrical.
The Fruit is on the female tree and is a heavy, woody cone containing small, black, egg-shaped Nuts enclosed within the cone scales. Hairs attached to the Seed form a wind dispersal mechanism. They act like a parachute. When the bracts open, the seeds are eventually dispersed by the wind. In some cases, it takes a fire to initiate.
Distribution & Ecology
This tree is Endemic (Endemism is the ecological state of a species being unique to a defined geographic location) in the RSA in winter rainfall areas of the Wetern Cape and grows on places such as Peninsula Granite Fynbos, Peninsula Shale Renosterveld, Cape Winelands Shale Fynbos, Swartland Shale Renosterveld, Boland Granite Fynbos. E.g. the eastern slopes of Table Mountain – below the Table Mountain sandstone. In these environments it is remarkable resilient against dry times, wind and even surviving mountain fires. Trees occur from somewhat above sea level to 330m high.
The Leaves are much sought after for floral arrangements. Plants are easily grown from Seeds. Outside the winter rainfall area, plant the trees on a slope, in an open “windy” area in acidic soil. Water the plants in the dry winters. As early as 1693, this plant was successfully grown in England. It is thus able to survive out of a winter-rainfall area. For Cone production, both male and female trees are necessary. Do not disturb the roots once they are established. After germination, trees take up to 7 years to Flower. Trees last for about 20 years and seeds remain viable for more than 75 years. Wood is soft and spongy and it was used for beams, box manufacture and as fuel. It is now a protected tree.
Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of Southern Africa, edn 3. Struik, Cape Town.
Palmer, E. & Pitman, N. 1972. Trees of southern Africa, Balkema, Amsterdam, Cape Town.