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by M. Ritter, J. Yost, W. Mark, J. Reimer
GENERAL INFO
Grevillea robusta timber was widely used for doors, windows, and musical instruments. Silk oak is not a true oak (Quercus spp.), but is a member of the Protea family, a Southern Hemisphere family that includes the proteas, banksias, and macadamia nut (Macadamia integrifolia). Silk oak is the largest of the 360 or so species of Grevillea—most of which are from Australia. It can grow up to 150 feet high. Silk oak s pale, pinkish wood, which is reminiscent of oak, is used for furniture, cabinets, door, windows, and musical instruments. This species is a fast-growing, spring blooming tree and reproduces vigorously in moist climates. It is an invasive weed in Hawai‘i, southern Florida, and other subtropical parts of the world. Grevillea robusta has a HPWRA (Hawai‘i Pacific Weed Risk Assessment) score of 8 (High Risk ).
Native range: Eastern AustraliaPotential invasiveness: This plant is classified as potentially invasive in specific areas of California by the California Invasive Plant Council (Cal-IPC).Horticultural use: HedgedEthnobotanical Info / Tree Use: This Australian native tree species has become economically important in agroforestry systems in India and Africa, where it is planted for its shade characteristics and hardwood value. The hardwood is widely used for construction, musical instruments, furniture, and window frames. The sawdust can produce dermatitis due to toxins in the wood. There are reports of Aboriginal peoples drinking the flower nectar mixed with water for a sweet beverage. The species was introduced to Hawaiʻi from Australia in 1880 for reforestation efforts, but has since naturalized and become a serious weed in the island’s mesic and wet forests. (Little, 1989; Ong et al., 2000) Citations Page
Native range: Eastern AustraliaPotential invasiveness: This plant is classified as potentially invasive in specific areas of California by the California Invasive Plant Council (Cal-IPC).Horticultural use: HedgedEthnobotanical Info / Tree Use: This Australian native tree species has become economically important in agroforestry systems in India and Africa, where it is planted for its shade characteristics and hardwood value. The hardwood is widely used for construction, musical instruments, furniture, and window frames. The sawdust can produce dermatitis due to toxins in the wood. There are reports of Aboriginal peoples drinking the flower nectar mixed with water for a sweet beverage. The species was introduced to Hawaiʻi from Australia in 1880 for reforestation efforts, but has since naturalized and become a serious weed in the island’s mesic and wet forests. (Little, 1989; Ong et al., 2000) Citations Page
TREE CHARACTERISTICS
Tree Shape: Conical or RoundedMaximum Tree Height: 60 feetCanopy Width: 60 feetGrowth Rate: ~36 in/yearLeaf Arrangement and Leaf Form: Alternate, Bipinnately CompoundLeaf Shape: LinearLeaf color: GreenFlowers: ShowyFlower Color: Orange or YellowFlower Time: SpringFruit: Medium Brown CapsuleFruiting time: FallBark Color: Dark Brown, FissuredLitter Type: Dry Fruit, Leaves, Twigs
SITE CONDITIONS
Recommended Planting Area: 4' to 7'Water Use Rating: LowSunset Climate Zone: 8 - 9, 12 - 24, H1, H2Shade Tolerance: NoUSDA Hardiness Zone: 8, 9, 10Soil Texture: Loam or Sand or ClaySoil pH: Slightly Acidic to Very AlkalineSalt Tolerance: moderateWind Resistance: Lowest
CONSIDERATIONS
Branch Strength: WeakRoot Damage Potential: ModeratePotential health issues: IrritantWildlife interactions: Attracts bees, birdsDisease and Pest susceptibility: Phytophthora, Root Rot and ScalesDisease Resistance and Pest Resistance: Armillaria, Root RotUtility Friendly: NoWCISA Appraisal: Suggested LCANT 24" box, Suggested LCANT 24" box, Group Rating 2, Approx. cross sectional area 2.24 sq. in.
External Resources
CITE THIS TREE
"SelecTree. UFEI. "Grevillea robusta Tree Record." 1995-2025. Cal
Poly State University, San Luis Obispo. Accessed on Jun 1, 2025."
< https://selectree.calpoly.edu/tree-detail/678 >
< https://selectree.calpoly.edu/tree-detail/678 >
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