Silk Oak Tree
Grevillea robusta – Silk Oak
Other Common Names: Silkoak, Silver Oak, Australian Silky-oak, Silky Oak
Grevillea robusta is a fast-growing evergreen tree that belongs to the Proteaceae or Protea family. It is not related to true oaks, but is known by its common names such as Australian Silver Oak, Southern Silky Oak, Silky Oak, or simply Silk Oak.
It can grow between 18 to 35 meters or 59 to 115 feet tall, but usually shorter. It is considered as the largest plant in its genus as it can spread to 25 to 30 feet and the trunk diameter can go in excess of 1 meter or 3 feet. The outer bark of the trunk is gray, rough, and wrinkly, while the inner bark is orange to brown in color.
The single trunk has several branches that do not droop. The branches are rusty brown and hairy, especially when young. The odd-pinnately compound leaves are green in color and are arranged alternately. They generally grow from 15 to 30 centimeters or 6 to 12 inches long, while the leaf blades are usually 2 to 4 inches. They are lanceolate in shape and have grayish white undersides.
Silk Oak flowers grow in clusters on inflorescences that depict a bottlebrush. They bloom in the spring and grow between 8 to 15 centimeters or 3 to 6 inches long. They have no petals but they have a long calyx or sepal that has 4 lobes. The flowers are used in honey production as they have abundant sweet nectar that attracts birds to feed on it.
The flowers are followed by fruits or seed follicles, which contain 1 or 2 winged seeds. They are brown to black in color with a dry and hard covering, that is why they do not attract wildlife.