TreeRM

Silky oak

Grevillea robusta 路 Proteaceae 路 also Southern silky oak, Australian silver oak, Grevillea

A fast, upright semi-evergreen tree of 18 to 30 m (to 40 m at home) with fern-like silvery-backed leaves and golden toothbrush flowers full of nectar. In the East African highlands it is the smallholder's tree: lines of grevillea on field boundaries in Kenya, Rwanda, Uganda and Ethiopia give poles, firewood and timber without shading crops much. It is also invasive in places: South Africa lists it under NEMBA (Category 3 in the 2020 gazette; some sources cite 1b), Hawaii rates it High Risk, and it naturalises in Florida and elsewhere.

Broadleaf evergreenFast growingFull sunLow water
Silky oak
Wikimedia Commons, file Grevillea_robusta_Australia.jpg (see file page for author and licence)

Where it stands

Native

  • 馃嚘馃嚭 NSW, Australiasource
  • 馃嚘馃嚭 QLD, Australiasource

Adapted

  • 馃嚜馃嚬 Ethiopia 路 Exotic; widely plantedsource
  • 馃嚠馃嚦 India 路 Exotic; shade tree in tea and coffeesource
  • 馃嚢馃嚜 Kenya 路 The most widely planted farm boundary tree in the highlands; exotic per ICRAFsource
  • 馃嚪馃嚰 Rwanda 路 Exotic; widely plantedsource
  • 馃嚭馃嚞 Uganda 路 Exotic; widely plantedsource
  • 馃嚭馃嚫 FL, United States 路 Introduced per WCVP; not on FISC listsource

Invasive

  • 馃嚭馃嚫 HI, United States 路 HPWRA score 8, High Risk; naturalisedsource
  • 馃嚳馃嚘 South Africa 路 NEMBA 2020 national list: Australian silky oak, Category 3 (may not be propagated, sold or planted; existing trees may remain); African Legacy cites Category 1b, so check the current gazettesource

Care

Plant at the start of the rains on drained soil; grows 2 to 3 m a year when young. Pollard or lop repeatedly for poles and to reduce shading of adjacent crops; it resprouts well and suckers from roots. Termites attack trees on dry sites; fungal leaf diseases hit over-watered nursery stock. Sap and sawdust cause dermatitis in some people; branches are brittle in wind.

Benefits

Fast canopyPollinatorsBirdsWindbreakDrought tolerantFlowers

Good for

AgroforestryTimberWindbreakStreet treeparks

Watch out for

Invasive elsewhereWeak woodAllergenic pollenHeavy litter