How to Grow Hawaiian Silk Oak

Wikimedia Commons

Hawaiian Silk Oak

Grevillea robusta

tree

Hawaiian silk oak is a fast-growing, evergreen tree native to Australia that features delicate, fern-like foliage and showy golden-orange flowers. Despite its common name, it is not related to true oaks and is prized as an ornamental specimen and shade tree in warm climates. The tree can reach 40-50 feet tall and produces attractive flowers that attract birds and pollinators.

When should you plant Hawaiian Silk 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.

Get my Hawaiian Silk Oak timeline →

Example Hawaiian Silk Oak timeline · Pittsburgh, PA (Zone 6b)

Plant Hawaiian Silk Oak
Around Apr 17

Near Pittsburgh's average last spring frost.
Tend & protect
Late spring–summer

Watering, feeding, and pest-watch reminders.
Harvest Hawaiian Silk Oak
Late summer into fall

Before the first fall frost (≈ Nov 8)

Sample dates for Pittsburgh, PA. Sign up to get exact Hawaiian Silk Oak dates for your own zip code.

Growing Conditions

☀️

Sun: Full sun, 6-8 hours daily; tolerates partial shade in very hot climates

💧

Water: Moderate watering; keep soil consistently moist but not waterlogged during establishment (first 2-3 years). Once established, drought-tolerant and requires minimal supplemental watering except during prolonged dry spells.

📏

Spacing: 240 inches

📅

Days to maturity: Not applicable (perennial tree); flowers appear within 3-5 years from seed

🌱

Planting depth: Same depth as root ball; surface sow seeds with light covering

Soil

Type: Well-draining sandy or loamy soil

pH: 6.0-7.0

Amendments:

Coarse sand or perlite for drainage improvement Organic compost for initial planting Mulch to retain moisture and regulate soil temperature

Growing Zones

Find your zone →

Thrives in zones 9b-11; can be grown in containers in cooler zones and moved indoors during winter

9b 10a 10b 11a 11b

Get my Hawaiian Silk Oak timeline →

Growth Stages

Seedling

3-6 months

Young plant with emerging true leaves; appears as a delicate upright shoot with finely divided foliage.

Maintain consistent moisture without waterlogging. Provide bright, indirect light initially. Protect from strong winds. Keep in warm location (60-70°F minimum).

Juvenile

1-2 years

Established young tree with increasing height and a more developed fern-like canopy; may be 2-6 feet tall.

Begin light pruning to establish desired shape. Continue moderate watering during dry periods. Gradually acclimate to full sun exposure. Support tall, leggy growth with staking if needed.

Vegetative Growth

2-4 years

Rapid height and spread development; tree becomes fuller with dense, feathery foliage; trunk thickens significantly.

Prune lower branches to develop clear trunk if desired for ornamental purposes. Water deeply but less frequently once established. Apply mulch around base. Minimal fertilization needed.

Flowering

2-4 months

Golden-orange, clustered flowers (bottlebrush-like spikes) appear at branch tips in spring and early summer; tree may reach mature height.

Maintain regular watering during blooming period to support flower development. Deadhead spent flowers if desired to encourage continuous flowering. Do not over-prune during flowering season.

Maturity

Ongoing; 20-30+ years

Full-sized tree with dense canopy, regular annual flowering, and potential seed pod development; strong branch structure.

Minimal maintenance required. Prune for shape and to remove dead wood. Monitor for pests. Provide occasional deep watering during drought. Tree provides significant shade.

Companion Planting

Plan your garden →

Plant with:

Bougainvillea Ixora Plumbago Lantana Bottle brush Bird of Paradise Desert rose

Avoid planting near:

Shallow-rooted plants that compete for nutrients Plants requiring acidic soil conditions Salt-sensitive ornamentals in coastal areas

Common Pests

Spray with water to dislodge; use neem oil or insecticidal soap in severe cases; maintain adequate humidity
Prune heavily infested branches; apply horticultural oil spray in dormant season; introduce natural predators like ladybugs
Use yellow sticky traps; spray neem oil or insecticidal soap; maintain healthy plant vigor through proper watering
Ensure excellent drainage; avoid overwatering; remove infected portions; apply fungicide if necessary; replant in well-draining soil
Remove affected leaves; improve air circulation; avoid overhead watering; apply fungicide if widespread

Uses

🏠

Ornamental Shade Tree

Household

The Hawaiian silk oak serves as an excellent shade tree for warm-climate gardens and landscapes, providing filtered shade with its delicate, feathery foliage. Its rapid growth and attractive form make it ideal for creating privacy screens or focal points in residential and commercial landscapes. [source]

🎨

Cut Flower Arrangements

Craft

The distinctive golden-orange bottlebrush-like flowers are striking in floral arrangements and bouquets, adding unique texture and warm color. Flowers can be used fresh or dried for lasting decorative displays. [source]

🦋

Pollinator and Bird Attraction

Wildlife

The abundant flowers are highly attractive to native bees, butterflies, and nectar-feeding birds, making it an excellent choice for supporting wildlife in the garden. The tree provides both food and shelter for numerous bird species. [source]

🏠

Timber and Wood Products

Household

The lightweight, attractive wood has been historically used in Australia for cabinetry, veneers, and decorative woodworking. In its native and cultivated regions, it provides valuable timber resources. [source]

💊

Traditional Botanical Uses

Medicinal

In traditional medicine systems of Australia and surrounding regions, various parts of Grevillea species have been used in herbal preparations, though scientific validation is limited. Modern interest focuses on potential antioxidant properties. [source]

This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.

Harvest Tips

Hawaiian silk oak is not harvested for food or traditional products. Flowers can be cut for ornamental arrangements when fully open. Seed pods may be collected in late summer for propagation purposes. Prune branches selectively for arrangement material in spring during peak flowering.

Fun Facts

🌱 Despite being called 'Hawaiian silk oak,' the Hawaiian silk oak is native to Australia, not Hawaii, and is not related to true oaks (Quercus species); the name reflects its popularity as an ornamental in Hawaii and its oak-like appearance.
🌱 The tree is remarkably fast-growing, capable of reaching 10-15 feet in just 3-5 years under ideal conditions, making it one of the fastest-growing trees suitable for ornamental use in warm climates.
🌱 The feathery, fern-like foliage is actually bipinnately compound leaves, which give the tree its distinctive delicate appearance and contribute to its ability to filter light effectively.

Gardening Terms

New to gardening? Learn about terms used in this guide:

Annual Deadhead Full Sun Mulch Partial Shade True Leaves

Shop Hawaiian Silk Oak plants and related plants at Plant Addicts →

Join 30,000 gardeners planning their gardens with LizPlants.

Get your personalized Hawaiian Silk Oak planting timeline

Tell us your zip code and we'll calculate exactly when to start Hawaiian Silk 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 Hawaiian Silk Oak timeline →