Banksia is a genus of 76 species in the plant family Proteaceae, named after the English botanist Sir Joseph Banks, of the Cook expedition in 1768. They are native to Australia, varying from prostrate shrubs to trees up to 25 m tall.
There are 76 Banksia species, and all but one occur naturally only in Australia. A number of Banksia cultivars have also been developed.
Western Australia contains the greatest diversity of banksias, with 60 species recorded. They are also an important part of the flora of Australia's eastern coast. Few banksias are found in the arid regions of Australia or in the rainforests of the northern coast.
There are no species which are common to both eastern and western Australia, except Tropical Banksia, Banksia dentata, which occurs across northern Australia, in Papua New Guinea, Irian Jaya and the Aru Islands.
The flower heads are made up of hundreds (sometimes thousands) of tiny individual flowers grouped together. The color of the flower heads usually ranges from yellow to red. Many species flower over autumn and winter.
The fruits of banksias (called follicles) are hard and woody and are often grouped together to resemble cones (which they are not; true cones are produced only by conifers). The fruits protect the seeds from foraging animals and from fire. In many species the fruits will not open until they have been burnt or completely dried out.
Banksias are easily propagated from seed. A common way to release seeds is to place the 'cone' in an oven at 120° to 140° C for about an hour. The follicles then open and the seeds can be removed with tweezers. Two black winged seeds are usually found in each follicle, together with a structure called a separator.
Insects sometimes lay their eggs in the flower buds and the larvae may eat the seed as it develops. A small hole in the woody fruit is usually a sign that this has happened and that the seed will not germinate.
Seeds should be sown in a very freely draining seed-raising mix which should not be allowed to dry out. As Banksia seedlings are prone to fungal attack, it is better to sterilise the seed-raising mix before planting. If this is not practical, very clean ingredients should be used.
Seedlings should be transplanted into small pots as soon as the first true leaves appear. A potting mix made from equal parts of river sand, loam and leaf mould (or peat moss) is generally suitable.
Despite being such a popular Australian plant, several banksias are listed as rare or threatened. Banksia brownii , the Feather-leaved Banksia, is named after the famous botanist Robert Brown (1773-1858) who accompanied Matthew Flinders to Australia. It is restricted to a few locations between Albany and the Sirling Ranges in Western Australia. Banksia verticillata , the Granite Banksia, is restricted to a few sites on or beside granite outcrops from Albany to Two Peoples Bay in Western Australia.
Banksias usually grow best in well drained soils in a sunny position. Most respond to light pruning, and those which form a woody rootstock (lignotuber) can be heavily pruned. Only low phosphorus fertilisers should be used.
Species native to Western Australia are prone to root-rot fungus and generally do not grow well in parts of Australia which experience high humidity and rainfall in the summer. Banksias range from low-growing shrubs to trees up to 25 m tall. Some species, for example Banksia ericifolia and Banksia menziesii , are known for their spectacular flower heads. The flower heads produce large volumes of nectar and attract many birds and small mammals to feed on them. Banksias are excellent plants to encourage native animals to the garden.