Banksia – an Australian icon

Australian Banksia Tree Seedpod CloseupBanksia is an Australian native evergreen tree or shrub in the protea family. Banksia’s namesake, Sir Joseph Banks, was the first to record its discovery when he and Daniel Solander landed on the east coast of Australia (then New Holland) on the Endeavour in 1770. Over the following decades various botanists would identify and name a few species, but it wasn’t until 1782 that Robert Brown, travelling with Matthew Flinders on the Investigator, discovered eleven new species of Banksia on the southwest coast of Australia. He would later find another two at Port Jackson, Sydney.

Since then the total number of recognised Banksia species has swelled to over 170. Fossils indicate that these species have likely existed for up to 50 million years, during which the plants survived massive climatic change as the land mass that would become Australia drifted from the southern tip of the globe up to its current location.

Characteristics

Banksia can range from small woody shrubs through to trees as tall as 25–30 metres. Shrubs may be erect or prostrate with stems at ground level, while trees usually have a stout, irregular trunk and low branches.

Banksia are best known for their unique elongated flower spikes and serrated leaves, though in more than half of the known species the flower spikes are much shorter, sometimes no more than a head. Each flower spike consists of a woody axis covered in hundreds or even thousands of tightly-packed pairs of flowers.

As the flower spikes or heads age, the flower parts dry up, darken in colour then gradually fade to grey, transforming into large, woody ‘cones’. Embedded within these cones are woody follicles enclosing one or two seeds. In some species these follicles release their seeds as soon as they are mature, but in many species the follicle only opens when burnt or dried, usually by bushfire.

Distribution

Banksia are endemic to Australia, with the exception of Tropical Banksia, which extends to New Guinea and the Aru islands, and one now-extinct species that was found in New Zealand. Over 90% of Banksia species are found in southwest Australia, with the remaining endemic species found in eastern Australia.

Most Banksia species thrive in the sandy soils of heathlands or low woodlands at mid-altitude, though there are exceptions. Some species can grow in heavier soils, rainforest, coastal areas, arid conditions, or high altitudes. Most can withstand dry and cold spells, though only one can survive with annual rainfall of less than 200 millimetres.

Though they can prosper in a wide array of Australian environments, many species are now threatened due to excessive land clearing, burning, and disease.

Ecological and cultural importance

Banksia produce large amounts of nectar and harbour insect larvae that provide a food source for many native wildlife, including birds, insects and small mammals. These animals are important pollinators for the species. The nectar has also been used by indigenous people, who either eat it straight from the flowers or soak it in water to make a sweet drink.

In addition to their ecological significance, Banksia’s bright and unusual flowers are important to the nursery and cut flower industries, and their wood and cones have been used for arts and crafts as well as woodwork. Both the shrub and tree forms of Banksia are commonly planted in parks and gardens for their beauty and ability to attract wildlife. Beekeepers sometimes grow them as a reliable source of nectar, particularly when other sources are scant.

Threats

Having evolved over 500 million years in the changing Australian climate, Banksia are naturally adapted to bushfires. In many species, fire stimulates follicles to open and release seeds, which then germinate in the ground and allow rapid regeneration. Many other species are known to have fire-tolerant ‘lignotubers’ that can resprout after a fire and/or a thick protective layer of bark. At first glance, Banksia would appear to be an easily sustainable wood.

However, while fully developed Banksia can tolerate and even benefit from occasional bushfires, arson or intentional burning poses a threat because seedlings and young plants are not yet sufficiently developed to tolerate fire. Councils, local communities and conservationists often have radically different ideas on the ideal frequency of burning to reduce fuel-load in the bush.

Most Banksia species can be infected with ‘dieback’, a water mould that causes plant roots to rot and prevents normal water and nutrient absorption. In many affected areas up to 70% of plants are infected, usually dying within a few years. Banksia’s roots are particularly vulnerable, and in Western Australia the disease has reached epidemic proportions. Unfortunately, efforts to treat dieback, including treatment with phosphite and phosphorous acid, have had limited success.

When choosing Banksia products, it is important to be aware of the endangerment of many of the species, and to purchase from a reliable source that promotes sustainable practices.

Woodworking

Banksia wood is reddish in colour and has an appealing grain. The wood has a variety of uses, including boat parts, cabinet panelling and small decorative items; however, it is prone to warping and hence its woodworking applications are somewhat limited. More commonly, it is the ‘cones’ that are used in to make attractive and distinctive ornamental pieces. Banksia cones are sought worldwide for their remarkable texture and appearance, which are unique to the genus. Cones can vary from 4 to 12 inches in length and 2.5 to 5 inches in diameter, but the large, solid cones of the Bull Banksia are used most frequently.

The interior of the cone consists of a central seed cavity surrounded by a woody core. Depending on the intended use, the exterior of the pods may be left rough or smoothed down through woodturning, a form of woodworking that involves cutting and shaping the wood while it rotates on a lathe. Similarly, the interior may be left in its natural form as a design feature, or covered in resin or inlay. The result is a range of different products to suit many different uses.