Silky Oak

~ Grevillea robusta ~

PROTEACEAE

The Silky Oak’s crown of fiery blooms makes for a momentous spring scene when haloed by the golden afternoon sun, nectar glistening and calling to the honey-munching birds. It’s known to be a popular nesting and roosting haunt because of its high-up protective canopy. Grevillea robusta is the largest of the Grevilleas, a genus rich in diversity with 452 species and subspecies; it sits beside the Waratah and the Banksia in the ancient Proteaceae family. The Silky Oak is also prized for its sexy ‘silky’ and ‘robust’ timber, which saw a huge decline in the tree’s population during the 20th century.

WHERE TO LOOK

Grevillea robusta can be seen along the eastern coast, congregating around the capital cities of each state due to the high numbers in cultivation. It’s actually considered a bit of a pest in New South Wales and Victoria. In the wild, it’s fairly rare, growing on the subtropical coast and near coastal ranges in dry rainforests, along riverbanks and in wet forest.

Locations → Queensland: Brisbane Botanic Garden Mount Coot-tha, Lake Samsonvale, K’gari (Fraser Island), Sunshine Coast hinterland, Main Range National Park, Springbrook National Park and Buderim Flora and Fauna Reserve.

FEATURES

This tall single-trunked Grevillea tree grows 10–40m with a dark grey, lace-like patterned trunk. It features long 10–30cm dark green and fern-like leaves with silky hairy veins and a silvery underside. It’s considered semi-deciduous, losing some of those leaves each winter and spring before flowering. The 10–15cm inflorescence of around 100 flowers resembles a giant toothbrush with bright orange bristles measuring 2cm tall. The fruit is a hard, smooth 20mm follicle containing two seeds.

FLOWERING SEASON

Spring and summer → These striking flowers can be seen from September to November.

PLANTING

Due to its fast-growing nature, these plants are very popular in cultivation and generally flower in two to three years. Seeds and plants are widely available online and in nurseries. If you want to harvest seed, it tends to ripen and disperse quickly on the tree. Collect seeds by taking a section of nylon stocking and placing it over the developing fruit follicles; the seeds will drop into the stocking bag after being released and can be saved for future planting. This whole process generally happens in summer. Seeds can take around two years to germinate without pre-treatment, but soaking in hot water for 48 hours will speed up the process. It can be potted in shade when young and planted out to enjoy and flower in full sun. It tolerates frost and drought (once established), but prefers a warm and humid climate. Plant beside the Flame Tree (see p. 171) for a floral fireworks display each spring.