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Grevillea robusta

Southern silky oak

Southern silky oak, silky oak, Australian silver oak (Eng); pino de oro, árbol del fuego, roble australiano (Spa); roure d'Austràlia (Cat).

Non-Native

DID YOU KNOW...? Canadian guitar maker Jean Larrivée usually makes his famous acoustic instruments with the wood of the southern silky oak.

DESCRIPTION

A generally evergreen tree that can lose its leaves if it gets too cold. In the Canary Islands it is usually more than 20 m tall, but it never reaches the 50 m recorded in its native lands. It has an almost pyramidal crown, although this is sometimes less well defined, and a thick, straight trunk up to 1 m in diameter. The bark is dark greyish brown, very cracked with age and it 'bleeds' easily when damaged. The leaves are alternate, compound, very large (15-30 cm long) and seem to be divided in a very complicated way. They are in fact divided into 11-23 leaflets (odd-pinnate) with pointed tips that are also lobate or divided to a certain degree, giving the impression that the leaf is bipinnate. On the upper side they are dark green and hairless, but on the underside they are tomentose and silvery-whitish green in colour, something that can be seen easily when the wind moves the foliage. From spring to summer this tree is full of showy, bright yellow to orange blooms. The flowers are hermaphroditic, very primitive, filamentous and have upright stamens. The blossoms face upwards on long grouped flower stalks, in 15 cm-long clusters that give it the appearance of a brush. The fruits are dry (follicle type), almost black in colour, and arched. They are up to 2 cm long and terminate in a thin curved hook. At the start of winter the fruits of the southern silky oak open spontaneously releasing one or two seeds surrounded by a papery wing that aids their dispersion by the wind.

ECOLOGY

A rapidly-growing species that adapts easily to any type of soil and climate, although it is somewhat sensitive to the cold when young. It prefers full sun exposure. In the Canary Islands, the specimens that have become established in the wild mainly come from landscaped areas in the lower zones of the midslopes, or medianías, where there is frequent human influence.

DISTRIBUTION

The southern silky oak is originally from Australia, specifically the wooded coastal zone in southern Queensland. In the Canary Islands this tree is very commonly seen in private gardens, parks and along streets, and it is one of the best-known proteaceae, a family typical of the southern hemisphere. Until very recently it was only known to have become established in the wild on Gran Canaria, but at the beginning of 2016 the scientific journal Collectanea Botanica also reported that it had become naturalised on the island of La Palma.