Red Silky Oak Grevillea banksii

Grevillea banksii is the wild species behind most of the big, red flowered garden grevilleas, and planting it gives you the original rather than a hybrid: a quick large shrub or small tree with deeply divided leaves, pale and silky underneath, and thick cylindrical spikes of deep red flowers through much of the year, peaking from winter into spring. Its natural range is coastal and near coastal Queensland, from around Ipswich and Brisbane north to the Yeppoon district, but it has been planted far beyond it because it flowers so freely and feeds so many birds, from small honeyeaters through to rainbow lorikeets.

The common name invites confusion with the true silky oak. Silky Oak is a forest tree for acreage; the red silky oak is a fraction of its size. In its upright form it can be trained as a single trunked feature tree or kept branched low as a big screening shrub, depending on how you prune it in the first few years. The species also has spreading shrub forms and low coastal forms that will never make a tree, so if a tree is the goal, train a plant that already has one strong leading stem.

Frost, clay and a short life

Full sun and free drainage are not negotiable. It does well in sandy coastal soils, on slopes and in raised beds, and struggles in heavy clay that stays wet after rain, where root rot takes it suddenly. Frost will cut back a young plant, though once it has a woody frame it shrugs off a light one, and in Melbourne and other cool districts it is worth a warm, sheltered position against a north wall. Water regularly for the first summer, then rely on rain with an occasional deep soak in a dry spell.

It grows fast and burns out comparatively early, sooner than most garden trees, so get a successor started nearby before it declines rather than counting on permanence. It is also the source of the skin problem the whole hybrid group is known for: Grevillea banksii contains tridecylresorcinol, the compound behind the allergic rash linked to many banksii hybrids, and it can raise an itchy, blistering dermatitis on sensitive people. Handle prunings and cut branches with gloves on and arms covered, and keep it away from paths, play areas and the edges of pools. The flowers and seed pods also contain hydrogen cyanide, so do not let children suck the nectar or eat the flowers, and keep dogs from chewing fallen pods.

The species or one of its offspring

Choose the species when you want height and a looser, more natural shape than the compact hybrids give. Robyn Gordon Grevillea, the most familiar of its offspring, stays a low, wide shrub for the front of a garden, while Grevillea banksii can make a tree you can stand under. For other native trees and shrubs to plant around it, see Australian Native Plants.

Training it as a tree or a screen

Decide on the shape early. For a small tree, choose the strongest upright stem as the leader and remove lower side branches gradually over two or three years, never all at once, so the trunk thickens as it rises. For a screen, do the opposite and tip prune every shoot after flowering so it branches from low down. Either way, make every cut where leaves remain below it. Feed only with a low phosphorus native fertiliser, lightly, in spring. Cutting off spent flower spikes tidies the plant, encourages more flowers and, because it stops seed from setting, leaves fewer pods on the ground for a dog to find. Fallen spikes are worth sweeping off paving too, where their sticky nectar makes the surface slippery after rain.

Choosing a size

This plant is available in 2 sizes, from 300mm up to 100L, priced from $309.00 to $629.00 per plant. The size shown is the pot the plant arrives in, which is the rootball, not the height of the plant. Every size here is established stock rather than a starter plant, so this line is intended for immediate effect rather than for growing on. Not sure which to choose? Read our guide to planting for birds.