Grevillea, Silk Oak

The Silk Oak is a strong, enduring tree that reaches a maximum height of 50 metres. However, such growth can be expected only in its native country, Australia. Although it grows quite fast, it will usually not exceed 13 metres, especially in Arriyadh. The tree has a conical, upright form. Fern-like, lacy leaves are shiny green on top and silvery below, while the showy orange flowers are borne in large clusters on the branches, usually when the tree is in a semi-deciduous state after the winter. Silk Oaks are considered evergreen, but foliage may be shed owing to cold, or when the new leaves appear. It will tolerate a wide variety of soils, but these should be well drained. Waterlogging and alkaline desert soils limit the speed of growth and cause iron chlorosis. The wood is brittle and wind exposure may cause branches to die back or break off. Propagation is by seed or cuttings. G. robusta is a background tree for use in parks and in public squares. A mature tree makes a picturesque silhouette against the sky. Heavy pruning is possible, but may spoil the columnar or pyramidal shape. It has toxic qualities. Grevilleas may sometimes cause painful skin irritation. Regular irrigation is necessary at first, but a mature tree is generally drought-resistant and requires a deep soaking every month or so. Heavy leaf litter in spring necessitates a lot of tidying up from lawns and paving, although it can be left as mulch on the soil. This tree is rarely seen in Arriyadh, although it has potential for planting in protected situations.