Southern Silky Oak Tree

Southern Silky Oak (Grevillea robusta) is the fastest way to put real shade over an acreage block or a wide suburban yard. In a garden it makes about 15m tall and 8m wide over ten to fifteen years, with ferny grey green foliage and, from late spring, golden orange toothbrush flowers along the upper branches. It is the largest grevillea in cultivation, and it earns its space through sheer speed.

Why you'll love it

• Fast, genuine shade. Few natives put on canopy this quickly. With water in the first two years it can add well over a metre of height a season.
• A honeyeater magnet. The orange flower combs are heavy with nectar and pull in lorikeets, honeyeaters and native bees for weeks.
• Tough once it is away. Drought tolerant, heat tolerant and untroubled by poor soil, so it copes on hard clay and thin sand alike.
• Fine textured foliage. The divided leaves cast dappled light rather than dense shade, so grass still grows beneath it.

Where it works best

Shade tree for larger blocks. Give it 8m of clear width and at least that much from the house. Planting it in a small courtyard is the most common mistake made with this tree.

Driveways and avenues. Space trees 8m to 10m apart. At that spacing the crowns meet overhead in about eight years without the trunks competing.

Windbreaks. Plant 5m apart in a row, or stagger two rows, to filter wind across an open paddock rather than block it.

Growing Southern Silky Oak in Australia

Position and climate. Full sun, always. It suits tropical, subtropical and warm temperate gardens and tolerates light frost only, so cold inland and southern districts with hard winter frost will damage young trees. Site it clear of powerlines from the start.

Soil. Not fussy. It grows on poor, shallow and compacted ground where other trees stall, and prefers soil that drains rather than one that stays wet. Work compost through the backfill on heavy clay.

Water and feed. Deep soak weekly through the first two summers to build a deep root system, then taper right off. Use a low phosphorus native fertiliser in early spring only. Rich feeding produces soft, brittle growth that snaps in wind.

Pruning. Formative pruning matters here. In the first three years remove competing leaders and lift the lower branches gradually to build a strong single trunk, while the cuts are still small.

What to expect when it arrives

It is grown in four sizes: 300mm and 400mm pots, and advanced 45L and 100L stock. The 300mm and 400mm trees arrive as young whips, well under head height, and are the value option given how fast this species grows. The 45L and 100L sizes come with a formed trunk and a season or two of head start.

Trees travel upright and are delivered Australia wide, with delivery from $29.95. Advanced and large stock is freighted at cost. Some leaf drop in transit is normal. Expect strong new growth within four to six weeks in warm weather, and first flowering at around five to seven years. Every plant is covered by our 30 day healthy plant guarantee.

Plant care guides and related reading

• Browse the full grevillea range
• Choosing trees for a driveway or avenue
• Compare fast growing shade trees
• Trees and shrubs for windbreaks
• Field-grown Southern Silky Oak Tree in specimen sizes

Common questions

How fast does Southern Silky Oak grow?

Quickly. With water through the first two summers, expect well over a metre of height a year while it is young, slowing as it approaches 15m. Growth is slower in cooler warm temperate gardens.

Is it too big for a suburban backyard?

For most standard blocks, yes. At roughly 15m tall and 8m wide it needs a large yard, a rural block or a verge. In a small garden choose a compact grevillea instead.

Does it drop a lot of litter?

It sheds fine leaf material steadily and drops spent flowers after the spring flush. That is easy to live with over a lawn, less so directly above a pool or gutters.