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Sunday, May 8, 2011
EYE - CATCHING SILK OAK TREE (GREVILLEA ROBUSTA) - INFORMATION AND USES
BAHEKAR, BEKKA, SHAHBLOOT, SILKY OAK, SOUTHERN SILKY OAK, GREVILLEA ROBUSTA
Grevillea robusta is a member of the Proteaceae family and as its name suggests is a hardy member of that genus, which is why it is used as rootstock for the less hardy types of grevillea. It has many names in many languages; the ones given above are its Urdu names. In English it is also known as River oak, Silk oak, Silver oak and Southern Silky oak. It gets the oak name because the wood from it looks like oak wood. It also has Latin synonyms: - Grevillea umbratica and Grevillea pectinata. It was names by Allan Cunningham after Charles F. Greville (1749-1809) who was one of the founders of the Royal Horticultural Society, London; because of its hardiness it got the Latin name robusta (robust).
In Uganda and East Africa generally, as well as in Brazil, India and Hawaii, it is used for shade in coffee plantations, and for the same purposes in tea plantations in India and Sri Lanka as it protects not only the coffee and tea plants but also the workers. It can grow to heights of between 25 and 40 metres and is very beautiful when in flower. The flowers look like huge furry orange-gold caterpillars crawling across the branches. They are full of nectar and the Aborigines in Australia to which it is native, drink it straight from the flowers, or make a drink from them. The flowers are said to be very rich in vitamin C, and attract honeybees. Because it sheds its leaves and flowers, a thick layer of leaf mulch can build up in the soil around the tree, and as this may go to a depth of 30-40 centimetres, it protects the soil and maintains its temperature. The leaves and twigs ar said to be rich in aluminium.
I came across this species of tree in Rawalpindi and it was clearly an old tree that had been planted many years ago. Bees are attracted to the flowers, but the flowers, fruit and seeds of the tree can cause skin irritation because of the cyanogenic compounds found in them; the leaves can also irritate the skin. Despite this, in Kenya the natives of the Kakamega Forest use the tree for medicinal purposes, which is a little unusual given that it is a non-native species. They use it to cure sore throats, earache, chest problems, flu and toothache, and there are also superstitions regarding it. However in Hawaii where it was also introduced it has come to be seen as invasive.
The wood from Grevillea robusta is used in parts of the world for fuel as it makes good charcoal and firewood, as well as being used to make furniture. It is thought that the gum which exudes from the tree when it is cut could be used for industrial purposes. Yellow and green dyes can be made from the leaves, and the flowers are used for their fragrance.
Some research has already been done on this tree and its properties but there is a lot more to be done before scientists can determine what it can be used for in terms of medicine. So far they have isolated his-resorcinols from it, striatol being the most potent, which may be a potential help for the cardiovascular system. The tree also contains grevillol a phenolic which resembles uroshiols the skin irritant in poison ivy. It also contains 5 alkylresorcinol glycosides, names Grevillosides G and H which are also being investigated. Who knows in what ways this tree can help us? Until we find out, I’ll continue to admire its beauty.