tree

Silky Oak

The Story

Plant Bio

Grevillea robusta, the silky oak, is a fast-growing evergreen tree native to eastern Australia, capable of reaching heights over eighty feet in warm climates. It develops a straight trunk and a pyramidal crown clothed in deeply divided, fern-like green leaves with silky, silver-pubescent undersides.

This species is distinguished by its dramatic, horizontal flower racemes that resemble golden-orange toothbrushes, which erupt along the branches in spring. It is highly drought-tolerant once established and serves as an exceptionally tough canopy tree in frost-free regions.

Uses & Benefits:

Grown for its striking, fern-like evergreen foliage and brilliant golden-orange toothbrush-shaped flowers.

Functions as a fast-growing windbreak or shade tree, and is highly resilient to drought once established.

Provides a rich source of nectar for hummingbirds, bees, and other beneficial pollinators.

Essentials

At a Glance

Plant Type

Tree

Height

1180"

Width

470"

Light

Full Sun, Partial Sun

Zones

9, 10

Water

Low

Humidity

Moderate

Lifespan

Long

Native To

Australia

Toxicity

Skin Irritant

Bloom period

Spring – Early summer

In flower about 4 months of the year

Planting

How to Grow

Select a planting site in full sun with deep, sharply drained sandy loam or loam soil.
Dig a hole twice as wide as the root ball and of equal depth, avoiding any soil amendments.
Settle the tree into the hole, backfill with native soil, and water deeply to settle the roots.
Irrigate regularly during the first growing season, then reduce watering to rely on natural rainfall.

Pro Tip

Never prune mature branches back into old, leafless wood; this species lacks dormant buds on older stems and hard cutting will disfigure or kill the tree.

Keep It Thriving

Care Guide

Do

Ensure the soil drains rapidly to prevent root rot.
Use low-phosphorus fertilizers formulated for native Australian plants if feeding is necessary.
Protect young trees from freezing temperatures during their first few winters.

Don't

Do not plant in heavy, waterlogged clay soils or low-lying areas.
Do not apply standard high-phosphorus garden fertilizers, which damage the root system.
Do not cut back into bare, woody branches when pruning.

Seasonal Care Calendar

Task	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Fertilize
Pest Check
Prune
Winter Prep

Watch Out For

Pests & Diseases

Common Pests

Common Diseases

In the Garden

Landscape Uses & Companions

Landscape Uses

Specimen TreeShade TreeWindbreakCoastal Garden

Companion Plants

Callistemon viminalis Anigozanthos flavidus Westringia fruticosa

Multiply

Propagation Methods

Good to Know

Common Questions

Silky Oak questions

What zones can Silky Oak grow in?

Silky Oak is hardy in USDA Zones 9–10. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.

When does Silky Oak bloom?

Silky Oak typically blooms in spring through early summer. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.

Does Silky Oak need full sun?

Silky Oak does best in full sun to part shade. In hot climates, afternoon shade keeps blooms fresher longer.

Is Silky Oak drought tolerant?

Yes — once established (usually after the first full season), Silky Oak handles dry spells with minimal watering. Water deeply its first year to build the root system that makes that possible.