Grevillea robusta A.Cunn. ex R.Br. 1830
pronounced: grev-ILL-ee-uh roh-BUSS-tuh
(Proteacrae – the waratah family)
common name: Silky Oak
Grevillea is named for Charles Francis Greville (1749–1809). He was a younger son of Francis Greville, 1st Earl of Warwick, and was a passionate gardener. He was a close friend of Sir Joseph Banks. Robusta is Latin, robustus, of oak, firm, solid, strong. The species was named in 1830 by the explorer and botanist Allan Cunningham.
Silky Oak is one of the most beautiful and useful of Australian timbers, so much so that Queensland forests have become virtually depleted of the species. It was used extensively for external doors and windows, as it is resistant to rot, and it was a very popular timber for furniture-making. There are now severe restrictions on the harvesting of this tree, and most timber now offered for sale as Silky Oak comes from another Queensland species, Cardwellia sublimis. A small amount of Grevillea robusta timber is imported from Brazil.
This is a fast-growing, single-stemmed tree, usually 20–30 m in height and about 80 cm DBH, but sometimes larger. It occurs in much of eastern Queensland and northern NSW. At sea level, its latitudinal range is 26–30ºS, but this is extended northwards at altitude – it was prolific in the rainforests of the Atherton Tableland until the 1960s, by which time it had almost entirely been removed by timber-getters. It is now relatively rare in its natural state. A silky oak tree has been planted in the nature strip in Gifford Street, Horseshoe Bay, near the entrance to Bluey’s Ranch. I have not seen this tree in flower – the flowers and fruits photographs were taken in Townsville.
The dark grey bark is furrowed in a lace-like pattern. Young branchlets are angular, ridged, and sometimes slightly hairy. The fern-like foliage is very distinctive: the leaves are 10–35 cm long and 9–15 cm wide, pinnate to bipinnate, green on the upper surface and pale and silky below. The bright orange flowers, about 2 cm long, are borne in many pairs along the flower spikes, in October to November. The fruits are 2-seeded follicles about 2 cm long, with a slender persistent style. Seeds have a papery wing around the brown ovate central seed body.
Grevillea robusta has been introduced to warm temperate, subtropical and tropical highland regions around the world since the mid- to late-19th century, and is widely planted in India, Sri Lanka, Central and South America, and many countries in Africa. The trees are used extensively as high shade for tea and coffee plantations, and are often pollarded to produce a spreading crown. When the trees are planted in forestry conditions, thinning of inferior trees is often carried out after 4 or 5 years to yield poles and firewood.
The Silky Oak is one of the food plants for the caterpillars of Australia's largest hawkmoth, Coequosa triangularis.
Photographs taken Horseshoe Bay and Townsville 2011
Page last updated 9th December 2016