Grevillea robusta
Silkoak
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Family: Proteaceae · Type: Tree · Not Native
Conservation status: Cal-IPC Yes
Grevillea robusta (Silkoak) is a non-native California tree in the Proteaceae family, recognized by Only Grevillea species naturalized in California, Australian Proteaceae family.
Silkoak is a naturalized perennial tree found in southern Coastal Ranges, southern California, and Peninsular Ranges on brush-covered hillsides and in canyons at elevations below 450 meters. Flowering from March to May, this plant produces orange and yellow flowers in one-sided inflorescences with spreading pedicels. Growing up to 30 meters tall with a distinctive branching structure, it develops a robust canopy with complex foliage. Its large compound leaves are 15 to 40 centimeters long, featuring pinnately divided leaflets that are green on top and silvery-hairy underneath. The fruit is flat and winged, containing one to two seeds with a persistent style.
Identification and appearance
Key characters: Only Grevillea species naturalized in California, Australian Proteaceae family
Habitat and range
Habitat: Escaped from cultivation, brush-covered hillsides, canyons
Elevation: < 450 m
California counties: Los Angeles, Orange, San Luis Obispo, Ventura, San Diego, Alameda, Santa Clara
Outside California: native to eastern Australia
Bloom period
Grevillea robusta blooms Mar-May.
Conservation status
Cal-IPC Yes
Frequently asked questions
Is Grevillea robusta native to California?
No. Grevillea robusta is not native to California (recorded as not native).
When does Grevillea robusta bloom?
Grevillea robusta blooms Mar-May.
Where in California does Grevillea robusta grow?
Grevillea robusta occurs in Los Angeles, Orange, San Luis Obispo, Ventura, San Diego, Alameda, Santa Clara, at elevations of < 450 m.
What plant family does Grevillea robusta belong to?
Grevillea robusta is in the Proteaceae family, genus Grevillea.
Is Grevillea robusta invasive in California?
Grevillea robusta is listed by Cal-IPC with an invasiveness rating of Yes.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.