Southern silky oak

Description

Grevillea robusta, commonly known as the southern silky oak, silk oak or silky oak, silver oak or Australian silver oak, is a flowering plant in the family Proteaceae. It is a tree, the largest species in its genus but is not closely related to the true oaks, Quercus. It is a native of eastern coastal Australia, growing in riverine, subtropical and dry rainforest environments. Grevillea robusta is a fast-growing evergreen tree with a single main trunk, growing to 5–40 m (20–100 ft) tall. The bark is dark grey and furrowed. Its leaves are fern-like, 10–34 cm (4–10 in) long, 9–15 cm (4–6 in) wide and divided with between 11 and 31 main lobes. Each lobe is sometimes further divided into as many as four, each one linear to narrow triangular in shape. It loses many of its leaves just before flowering. The flowers are arranged in one-sided, "toothbrush"-like groups, sometimes branched, 12–15 cm (5–6 in) long. The carpel (the female part) of each flower has a stalk 21–28 mm (0.8–1 in) long. The flowers are glabrous and mostly yellowish orange, or sometimes reddish. Flowering occurs from September to November and the fruit that follows is a glabrous follicle. Silky oak occurs naturally on the coast and ranges in southern Queensland and in New South Wales as far south as Coffs Harbour where it grows in subtropical rainforest, dry rainforest and wet forests. It is now relatively rare in its natural habitat but has been widely planted, including on Norfolk Island and Lord Howe Island. It has become naturalised in many places, including on the Atherton Tableland in Australia and in South Africa, New Zealand, Hawaii, French Polynesia, Jamaica and Florida. It is regarded as a weed in parts of New South Wales and Victoria, as "invasive" in Hawaii and as an "invader" in South Africa. Grevillea robusta was first formally described in 1830 by Robert Brown after an unpublished description by Allan Cunningham. The type specimen was collected by Cunningham on the eastern edge of Moreton Bay in 1827. Brown's description was published in Supplementum primum Prodromi florae Novae Hollandiae. The specific epithet (robusta) is a Latin word meaning "strong like oak" or "robust".