# Silky oak (Grevillea robusta)

> 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.

Source: https://treerm.org/trees/grevillea-robusta · Updated 2026-11-08 · License CC BY 4.0

## Facts

- Also called: Southern silky oak, Australian silver oak, Grevillea
- Family: Proteaceae
- Type: Broadleaf evergreen
- Mature height: 25 m; spread 12 m
- Growth: Fast growing; lives about 100 years
- Light: Full sun
- Water: Low water
- Soil: Loam preferred; also clay loam and sand, mildly acid to neutral, free of waterlogging
- Native range: Native to riverine and vine forest of subtropical eastern Australia in south-east Queensland and north-east New South Wales; planted throughout the tropics and subtropics.

**Benefits:** Fast canopy, Pollinators, Birds, Windbreak, Drought tolerant, Flowers

**Good for:** Agroforestry, Timber, Windbreak, Street tree, parks

**Watch out for:** Invasive elsewhere, Weak wood, Allergenic pollen, Heavy litter

## 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.

## Where it stands

- **Native:** NSW, Australia; QLD, Australia
- **Adapted:** Ethiopia (Exotic; widely planted); India (Exotic; shade tree in tea and coffee); Kenya (The most widely planted farm boundary tree in the highlands; exotic per ICRAF); Rwanda (Exotic; widely planted); Uganda (Exotic; widely planted); FL, United States (Introduced per WCVP; not on FISC list)
- **Invasive:** HI, United States (HPWRA score 8, High Risk; naturalised); South Africa (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 gazette)

## Sources

- https://apps.worldagroforestry.org/treedb2/speciesprofile.php?Spid=921
- https://apps.worldagroforestry.org/treedb/AFTPDFS/Grevillea_robusta.PDF
- https://faolex.fao.org/docs/pdf/saf220858.pdf
- https://www.africanlegacy.org.za/alien-plant/grevillea-robusta-australian-silky-oak
- https://plantpono.org/hpwra/grevillea-robusta/
- https://www.gbif.org/species/2891791