Silver banksia

Sun

Full sun is best; tolerates light partial shade but flowers less freely.

Water

Water regularly during establishment, allowing the surface soil to dry between waterings. Established plants tolerate dry spells, but prolonged drought may require occasional deep watering.

Soil

Well-drained, acidic to neutral soil with low phosphorus levels. Sandy loam is ideal; avoid waterlogged ground and strongly alkaline soil.

Height

Usually 6-30 ft (1.8-9 m), depending on provenance; some forms remain smaller.

Spread

Usually 6-20 ft (1.8-6 m), depending on form.

Flowers

Pale yellow to golden cylindrical flower spikes, usually from late summer through winter, sometimes into spring; timing varies with climate and provenance.

Foliage

Evergreen. Narrow, leathery green leaves with conspicuously silvery-white undersides; margins may be toothed or nearly smooth.

Growth

Moderate in suitable conditions.

Care needed

Low

• Pollinators
• Drought tolerant
• Heat tolerant
• Wildlife
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Hard

Toughness

Needs looking after

Pick your zone, country, light and whether you have pets.

1. Planting day

   2.1 ft (0.65 m)

2. After 1 year

   5 ft (1.6 m)

3. After 2 years

   8 ft (2.5 m)

4. After 3 years

   11 ft (3.5 m)

5. After 5 years

   18 ft (5.4 m)

   full size

About 5 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Native to

Australia

Growth rate

Moderate

• Plant in spring in frost-prone districts, or autumn in mild climates, with the root crown at soil level.
• Water deeply through the first one or two growing seasons; avoid keeping the root zone constantly wet.
• Use no fertilizer unless needed; if feeding, choose a low-phosphorus product formulated for Australian native plants.
• Apply a light layer of coarse mulch, keeping it clear of the trunk.
• Protect young plants from severe frost and choose locally proven stock where winters are cold.

Pruning. Lightly trim young plants after flowering to encourage branching, and remove dead or damaged growth when needed. Avoid hard cuts into bare old wood: the ability to reshoot varies between forms.

Spring

Plant in colder districts once severe frost has passed; water thoroughly and mulch lightly.

Summer

Check new plants during dry spells and water deeply when the root zone begins to dry.

Late summer

Inspect foliage for yellowing and check drainage and fertilizer use before adding nutrients.

Autumn

Plant in mild-winter districts while the soil is still warm and seasonal rain is returning.

Winter

Keep roots free of standing water and protect young plants during unusually hard frosts.

After flowering

Lightly shorten leafy shoots if shaping is needed; retain some old flower spikes for their woody seed cones.

• Use a tree-form specimen as a small evergreen focal point, allowing room for its natural crown.
• Plant shrubby forms in an informal screen with other low-phosphorus-tolerant Australian natives.
• Combine with tussock grasses and mat rushes in a coastal or gravel garden for contrasting leaf textures.
• Place near a seating area where visiting nectar-feeding birds and the silvery leaf undersides can be seen.

Garden styles it suits: Australian native, Coastal, Wildlife garden, Dry gravel garden, Low-maintenance and Architectural minimal.

Plant it with: Spiny-headed mat rush, Kangaroo grass, Common everlasting, Coastal rosemary, Common correa and Prickly tea-tree.

Wildlife: Nectar-rich flowers attract honeyeaters in Australia, as well as bees and other insects. Birds may take seeds from the woody cones, and dense shrubby forms provide shelter.

• Phytophthora root rot: prevent with excellent drainage, clean nursery stock and careful watering; remove badly affected plants rather than replanting another susceptible banksia in the same wet spot.
• Phosphorus toxicity: avoid ordinary high-phosphorus fertilizers; stop feeding if leaves develop unexplained yellowing, browning or dieback.
• Yellow leaves on alkaline soil: check soil pH and drainage; use an appropriate iron treatment for temporary relief, but choose a more suitable site if the soil is strongly alkaline.
• Scale insects: inspect stems and leaf undersides; prune small infestations out or apply a labelled horticultural oil, avoiding hot weather and open flowers.

Not known to be toxic to people, cats, dogs or horses, and no particular part is established as poisonous. Specific animal-safety information is limited; do not encourage pets or livestock to eat the foliage or woody cones.

• Coast banksia (Banksia integrifolia)

  Usually has larger leaves arranged in conspicuous whorls, with mostly smooth adult leaf margins; silver banksia generally has smaller, scattered leaves.

• Saw banksia (Banksia serrata)

  Has much larger, coarsely saw-toothed leaves and thick, rough bark; silver banksia has narrower leaves with smaller teeth or smooth margins.

• Heath banksia (Banksia ericifolia)

  Has very short, needle-like leaves and usually orange to reddish flower spikes, rather than the broader, silver-backed leaves and pale yellow flowers of silver banksia.

Banksia honours botanist Sir Joseph Banks, while marginata refers to the leaf margins and the common name describes the silvery leaf undersides.

Propagation. Sow seed into a free-draining, low-phosphorus seed mix and keep moist but not saturated. Seedlings vary in size and habit; cuttings can preserve selected forms but are less straightforward and may root inconsistently.

Accepted botanical name

Banksia marginata

Native range

New South Wales, Tasmania and Victoria.

Measured

Average height 500 cm.

Sources: GBIF (CC BY 4.0) and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.