How to Grow Silky Oak
Wikimedia Commons
Silky Oak
Grevillea robusta
treeGrevillea robusta, commonly known as Silky Oak, is a fast-growing evergreen tree native to Australia valued for its feathery, fern-like foliage and striking golden-yellow bottlebrush-like flower clusters. It is highly ornamental and serves as an excellent shade tree, screen plant, or specimen tree in warm climates. The tree can reach 30-50 feet tall and is also popular as a large indoor potted plant in cooler regions.
When should you plant Silky Oak in your zone?
Get a personalized planting timeline — when to start seeds, transplant, and harvest — based on your USDA zone and local frost dates. Free to start.
Example Silky Oak timeline · Pittsburgh, PA (Zone 6b)
-
Plant Silky Oak
Around Apr 17Near Pittsburgh's average last spring frost.
-
Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
-
Harvest Silky Oak
Late summer into fallBefore the first fall frost (≈ Nov 8)
Sample dates for Pittsburgh, PA. Sign up to get exact Silky Oak dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in USDA zones 9b-11; tolerates frost to about 25°F (-4°C) when established
Sign up free to see if Silky Oak grows in your zone — and get a personalized planting timeline.
Get my Silky Oak timeline →Growth Stages
Seedling & Establishment
6-12 monthsYoung plant with delicate, finely divided fern-like foliage; small size with minimal branching
Provide regular watering to establish taproot; protect from strong winds; stake if necessary; mulch base; fertilize lightly monthly during growing season
Vegetative Growth
1-2 yearsVigorous upright growth with increasingly feathery, light green foliage; rapid height and spread gain; no flowers yet
Water consistently during drought; prune lower branches if desired; thin competing stems; apply balanced slow-release fertilizer annually; remove any frost-damaged growth
Pre-flowering
6-12 monthsTree develops mature form with fuller canopy; foliage becomes slightly darker and more leathery; flower buds begin forming
Reduce nitrogen fertilizer to encourage flowering; maintain consistent watering; prune to shape as desired; thin interior branches for air circulation
Flowering
3-4 months (spring/early summer, with occasional repeat blooms)Spectacular golden-yellow to orange-red cylindrical flower clusters (6-8 inches long) appear at branch tips, attracting birds and pollinators
Maintain regular watering during bloom; deadhead spent flowers if desired to encourage more blooms; avoid heavy pruning during flowering; observe for spider mites in dry climates
Maturity & Maintenance
Ongoing; trees live 50+ yearsEstablished tree with full canopy, reaching 30-50+ feet; regular annual flowering; strong, deep root system
Minimal fertilizer needed once established; drought-tolerant but performs better with occasional deep watering; light annual pruning to maintain shape; monitor for pests; every 2-3 years apply balanced fertilizer in spring
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
-
Increase humidity with misting; spray with neem oil or insecticidal soap in early morning; prune heavily infested foliage; maintain adequate watering to reduce stress
-
Remove with soft brush or cloth; spray with horticultural oil in winter dormancy; treat with neem oil monthly if severe
-
Spray with strong water jet; apply insecticidal soap; use neem oil; encourage beneficial insects like ladybugs
-
Yellow sticky traps; spray undersides of leaves with insecticidal soap; neem oil applications; increase air circulation
-
Ensure excellent drainage; avoid overwatering; remove affected plants; improve soil aeration; apply fungicide if caught early
Uses
Cut flowers & floral arrangements
HouseholdThe striking golden-yellow bottlebrush flower clusters are excellent long-lasting cut flowers for arrangements and can be dried for dried flower displays. [source]
Nectar source for birds and pollinators
WildlifeFlowers attract hummingbirds, honeyeaters, sunbirds, and native bees, making it a valuable plant for wildlife gardens and bird-watching areas. [source]
Ornamental shade and specimen tree
HouseholdThe feathery foliage and fast growth make it ideal for screening, windbreaks, or as a focal point tree in warm-climate gardens and landscapes. [source]
Indoor container plant
HouseholdIn cooler climates, Grevillea robusta is grown in large pots indoors or in conservatories, valued for its elegant fern-like foliage and manageable size when confined. [source]
Reforestation and environmental restoration
HouseholdNative to Australia, Grevillea robusta is used in tropical and subtropical regions for reforestation projects and erosion control due to its fast growth and deep root system. [source]
Harvest Tips
Grevillea robusta is not harvested for food or material; instead, enjoy its ornamental flowers by cutting 6-8 inch stems for floral arrangements. Cut flowers last 1-2 weeks in water. Collect dried seedpods for craft projects if desired. Prune lightly after flowering to maintain shape, removing dead wood and crossing branches.
Fun Facts
- 🌱 Grevillea robusta is native to the rainforests of northeastern Australia and is the floral emblem of Queensland State.
- 🌱 The common name 'Silky Oak' refers to the silky texture of the feathery leaves, though it is not actually an oak tree; it belongs to the Proteaceae (protea) family.
- 🌱 The tree grows remarkably fast—often 3-4 feet per year in ideal conditions—making it one of the fastest-growing ornamental trees in warm climates.
Gardening Terms
New to gardening? Learn about terms used in this guide:
Join 30,000 gardeners planning their gardens with LizPlants.
Get your personalized Silky Oak planting timeline
Tell us your zip code and we'll calculate exactly when to start Silky Oak seeds, transplant seedlings, and harvest — based on your USDA zone and local frost dates. Includes calendar reminders and printable task lists. Free to start.
Get my Silky Oak timeline →