GREVILLEA robusta (Silky Oak)

Silky Oak (Grevillea robusta) is the fastest way to put a real shade tree over an Australian garden. In cultivation it reaches roughly 10m to 15m tall and 6m wide within ten to fifteen years, carrying fine fern like foliage and, from spring, golden orange toothbrush flowers that draw honeyeaters and lorikeets from a distance. Supplied ex ground as a field grown specimen, it starts life in your garden already large.

Why you'll love it

• Fast, useful shade. Few Australian natives put a canopy over a driveway or a paddock in as few seasons as this one.
• Flowers birds cannot ignore. Orange and yellow flowers in spring bring honeyeaters and lorikeets into the garden in numbers.
• It grows where others sulk. Poor soil, drought, heat and reflected heat are all handled once the roots are down.
• Fine textured foliage. The divided fern like leaves cast dappled shade, so grass and understorey planting survive beneath it.

Where it works best

Shade trees. One tree over a lawn, a shed or a paddock corner does the work of several smaller trees. Allow at least 6m of clear width and keep it well back from the house.

Driveways and avenues. On a rural entrance or a long drive, space trees 8m to 10m apart so the canopies meet without crowding at maturity.

Windbreaks. A staggered double row at 8m spacing filters wind across an open block, which is more effective than a solid wall of foliage.

Feature planting. On an acreage block a single mature silky oak becomes the landmark tree of the property.

Growing Silky Oak in Australia

Position and climate. Full sun and open space. It suits tropical, subtropical, warm temperate and arid to semi-arid gardens, and it takes light frost only, so cool temperate districts and hard frosting inland gardens are not the place for it.

Soil. It tolerates poor and shallow soils that defeat most shade trees, but it does need drainage. The root system is large and vigorous, so plant it a long way from pipes, paving and building footings.

Water and feed. Water deeply and often through the first two summers, since an ex ground tree has lost part of its root system. After that it is genuinely drought tolerant. Use a low phosphorus native fertiliser in early spring, and nothing stronger.

Pruning. Form the tree early by removing competing leaders and lifting the lower branches for clearance. Mature trees need little beyond removing dead wood.

What to expect when it arrives

This is ex ground stock, sold as a single advanced size. The tree is grown in the field, then lifted with a root ball and prepared for transport, which usually means it is pruned back and carries less canopy than it did in the ground. That is normal practice and the tree rebuilds quickly.

Have the planting hole dug before it arrives, plant it the same day if you can, stake it against wind and water it deeply from the outset. Trees are delivered Australia wide, and advanced and large stock is freighted at cost. A minimum order of $300 before delivery applies, and every plant carries our 30 day healthy plant guarantee.

Plant care guides and related reading

• Read the full grevillea care guide
• Browse other ex ground trees
• Compare the wider grevillea range
• See more fast growing shade trees

Common questions

How close to the house can I plant it?

Not close. Give it at least 10m from footings, paving and pipes, because both the canopy and the roots are large and vigorous. It is a tree for open ground, not a courtyard.

How fast does it actually grow?

Quickly in warm conditions with water, often more than a metre a year while young. Growth slows once the tree is established at 10m or so.

Does it cause any irritation?

The foliage and the sawdust can irritate skin, so wear sleeves and gloves when planting or pruning. It is a reaction to handling rather than a hazard from standing under the tree.