Banksias are popular garden plants although the majority of species native to Western Australia are generally difficult to maintain for any length of time in areas of high summer humidity and rainfall (such as the eastern coastal strip of Australia). With many different forms, growth habits and flower colours, banksias can be used for many different purposes in the garden. In addition, the flowers of all banksias produce nectar and are excellent for attracting birds.
|Proteoid roots can often be seen by carefully removing a proteaceous plant from its pot, as shown here.
Photo: Brian Walters
Like most members of the Protea family, banksias have a distinctive root system ("proteoid roots") consisting of tight groupings of many small "rootlets". These are believed to enable the plants to more efficiently take up nutrients from the nutrient-deficient soils where many of the species occur naturally. In cultivation this means that the plants can be adversely affected by fertilizers, particularly phosphorus. It is generally recommended that banksias and other Proteaceae be fertilised only with low-phosphorus, slow-release fertilisers or not be fertilised at all.
Although a few Banksia species occur naturally on the margins of swamps, in cultivation all species perform best in well-drained soils and generally resent continually wet soils. Shallow clay soils can present problems but if garden beds are built up to 300-600mm, greater success is experienced. Banksias are generally at their best in open, sunny positions although the plants will tolerate some shade but probably with reduced flowering.
Like many plants, a number of Banksia species are susceptible to the root rot fungus, Phytophthora cinnamomi. This has caused serious environmental problems in some natural stands of native flora (including banksias) in Western Australia. The most dramatic effect of Phytophthora is the sudden demise in a matter of days of an apparently healthy plant. Improvement of soil drainage is the best means of minimising attack in areas where Phytophthora is known to exist.