Silk Oak

Grevillea robusta, commonly known as the silk oak, southern silky oak or silky oak, or Australian silver oak, is the largest species in the genus Grevillea of the family Proteaceae. It is not closely related to the true oaks, Quercus. It is a native of eastern coastal Australia, in riverine, subtropical and dry rainforest environments receiving more than 200 inches per year of average rainfall.
It is a fast-growing evergreen tree, between 59–115 feet tall, with dark green delicately dented bipinnatifid leaves reminiscent of a fern frond. It is the largest plant in the Grevillea genus, reaching trunk diameters in excess of 3 feet. The leaves are generally 6–12 inches long with greyish white or rusty undersides.
Its flowers are golden-orange bottlebrush-like blooms, between 3–6 inches long, in the spring, on a 2–3 cm long stem and are used for honey production. Like others of its genus, the flowers have no petals, instead they have a long calyx that splits into 4 lobes. The seeds mature in late winter to early spring, fruiting on dark brown leathery dehiscent follicles, about 2 cm long, with one or two flat, winged seeds.
Before the advent of aluminium, Grevillea robusta timber was widely used for external window joinery, as it is resistant to wood rot. It has been used in the manufacture of furniture, cabinetry, and fences. Owing to declining G. robusta populations, felling has been restricted.
Recently G. robusta has been used for side and back woods on guitars made by Larrivée and others, because of its tonal and aesthetic qualities.
When young it can be grown as a houseplant where it can tolerate light shade, but prefers full sun as it grows best in warm zones. If planted outside, young trees need protection on frosty nights. Once established it is hardier and tolerates temperatures down to 18 °F). It needs occasional water but is otherwise fairly drought-resistant.
Grevillea robusta is often used as stock for grafting difficult-to-grow grevilleas.
The tree has been planted widely throughout the city of Kunming in south-western China. forming shady avenues. Likewise, it is the primary shade tree lining the parkways of Euclid Avenue north of Foothill Blvd. in Upland.
This plant has gained the Royal Horticultural Society’s Award of Garden Merit.
G. robusta is also grown in plantations in South Africa and can also be grown alongside maize in agroforestry systems.
G.. robusta is naturalized in Hawaii, with invasive tendencies.
The flowers and fruit contain toxic hydrogen cyanide. Tridecylresorcinol in G.robusta is responsible for contact dermatitis.

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