Banksia penicillata is a medium to large shrub which can reach a height of 3-4 metres by a 3 metre spread. It generally has a single smooth barked trunk to 1 metre before branching. The species is nonlignotuberous, that is, the plants do not have a woody, underground structure that can produce new shoots. As a result they rely on seed to regenerate after fire.
The leaves are elliptical in shape, deep green on top and silvery below and usually have serrated margins on the mature foliage. The hairy new growth is attractive – being brownish or reddish in colour. The flowers occur in narrow spikes which are typically about 60 – 190 mm long, 60 mm wide and pale yellow in colour when fully open. The distinctive flower buds are highly variable in colour, with deep brown, chestnut, pink, greenish and even slate blue-grey reported. The seeds are enclosed in follicles attached to a woody cone and are generally retained within the cone until burnt.
When walking in the bush, the multicoloured inflorescences are often easy to miss as they blend in well with the foliage. Some people are also very aware of their musky sweet smell (while others are unable to detect any odour at all!). This leads to speculation that the flowers are designed for mammalian rather than avian pollination (and certainly possums, bats and native rats and mice are known to feed on them).
Previously this species was regarded as a subspecies of Banksia conferta which occurs in Queensland and in a small population near Taree in New South Wales. The most obvious difference between the two species is the bark – rough and tesselated on B.conferta; smooth on B.penicillata. The leaf margins of B.conferta are usually entire and undulating (usually serrated on B.penicillata).
B.penicillata has been in cultivation for only a relatively short time but is proving to be reliable in temperate and sub-tropical climates on well drained soil. The attractive foliage, new growth and unusual colors in bud are its best features horticulturally. It is best suited to full sun or dappled shade and should be useful as a densely foliaged screening plant.
B.penicillata is closely related to B.paludosa, especially subspecies astrolux from Nattai National Park near Mittagong in NSW. Indeed, the Nattai banksia was originally thought to be B. penicillata until examined more closely. Forms of Banksia paludosa generally have narrower inflorescences (40mm diameter) with open rather than crowded individual flowers in bud, and new growth lacks the reddish hairs of the subspecies of B.conferta.
Propagation from seed or cuttings is relatively easy.
* EPBC Act = Environment Protection and Biodiversity Conservation Act 1999;
ROTAP = Rare or Threatened Australian Plants (Briggs and Leigh, 1988)
For further information refer the Australian Plants at Risk page
Photo: Brian Walters