SelecTree: Tree Detail

SILK OAK TREE
Grevillea robusta

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Photo Locations: Kona, HI, Strybing Arboretum - San Francisco, CA, Los Angeles County Arboretum - Arcadia, CA, Cal Poly Campus - San Luis Obispo, CA and Lotusland - Santa Barbara, CA

General Notes

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 to the Eastern coast of Australia.

A Grevillea robusta in Riverside, CA is registered as a California Big Tree. It measures 112 feet high, with a trunk circumference of 196 inches and a crown spread of 45 feet.

Family: Proteaceae

Additional Common Names

SILK OAK TREE, SILVER OAK, OKA KILIKA, HAIKU KEOKEO

Tree Characteristics

Erect and requires ample growing space.

Conical or Rounded Shape.

Has Evergreen foliage.

Height: 50 - 65 feet.

Growth Rate: 36 or More Inches per Year.

Longevity 50 to 150 years.

Leaves Pinnately Compound with toothed leaflets to Bipinnately Compound, Green, No Change, Evergreen.

Flowers Showy. Orange or Yellow. Flowers in Spring. Has perfect flowers (male and female parts in each flower).

Brown Capsule, Medium (0.50 - 1.50 inches), fruiting in Fall.

Bark Dark Brown, Fissured.

Shading Capacity Rated as Dense in Leaf.

Litter Issue is Dry Fruit, Leaves and Twigs.

Tree Site Conditions & Constraints

Sunset Zones 8, 9 and 12 - 24; H1, H2.

USDA Hardiness Zones 8 - 10.

Exposure Full Sun.

Moist to Dry Soil.

Drought tolerant.

Clay, Loam or Sand Texture.

Slightly Acidic to Highly Alkaline Soil pH.

Salinity Tolerance is Moderate on Coast.

Seaside Tolerance is Good in Mild Zone.

Pests & Disease Information

Susceptible to Scales, Phytophthora and Root Rot.

Health, Safety & Environmental Concerns

Branch Strength Rated as Weak.

Root Damage Potential Rated as Moderate.

Irritant Health Hazard.

Attracts Birds and Bees.

Not Deer Palatable.

Special Uses & Values

Hedged.

Cite this tree:
SelecTree. "Grevillea robusta Tree Record." 1995-2020. Aug 14, 2020.
< https://selectree.calpoly.edu/tree-detail/grevillea-robusta >

This tree is not part of the SelecTree Nursery Connection. If you would like to see this tree listed, or know of a nursery that sells it, please contact us at ufei@calpoly.edu.