Coastal Banksia

B. integrifolia is a highly variable species. It is most often encountered as a tree up to 25 metres (82 ft) in height, but in sheltered locations it can reach 35 metres (115 ft). In more exposed areas it may grow as a small, gnarled tree, reaching to no more than about 5 metres (16 ft), and in highly exposed positions, such as on exposed coastal headlands, it may even be reduced to a small shrub. The tree usually has a single stout trunk, which is often twisted and gnarled, with the rough grey bark characteristic of Banksia. The leaves are dark green with a white underside, and occur in whorls of three to five. Adult leaves have entire margins. George specifies their dimensions as 4–20 cm (1.6–7.9 in) long and 6–35 mm (0.24–1.38 in) wide, but The Banksia Atlas warns that "Atlas contributors found great variability in these measurements with specimens often falling outside the varietal limits specified by George (1981) or being intermediate between two varieties." Juvenile leaves have dentate margins with a few short teeth, and are generally larger than adult leaves. Flowers occur in Banksia's characteristic "flower spike", an inflorescence made up of several hundred flowers densely packed in a spiral around a woody axis. This is roughly cylindrical, 10–12 cm (3.9–4.7 in) high and 5 cm (2.0 in) wide. …

B. integrifolia is widely distributed, in both geographical and ecological terms. According to Alex George, "it spans a wider geographical and climatic range than any other species." Thiele and Ladiges make a similar claim: that its distribution "is a broader latitudinal, altitudinal and ecological amplitude than any other species, with the possible exception of B. spinulosa." No other species of tree occurs closer to the coast at Cape Byron, making B. integrifolia the most easterly tree on the Australian mainland.

It occurs along almost the entire eastern coast of Australia, from Geelong, Victoria to Proserpine, Queensland. There was an isolated population on Long Island, Tasmania in 1999, and an 1876 record allegedly from King Island, although there has been speculation that that specimen was actually collected in the Furneaux Group. The species no longer occurs at any of these Tasmania locations, and has been declared extinct in Tasmania under that state's Threatened Species Protection Act 1995. The range of latitude is thus about 20° to 38°S. For most of its distribution, B. integrifolia occurs only within about 50 km (31 mi) of the coast, where it typically occurs on poor quality sandy soils derived from sandstone. It grows near coastal cliffs and headlands, alongside river estuaries, and even on stabilised sand dunes. …

Like most other Proteaceae, B. integrifolia has proteoid roots, i.e., roots with dense clusters of short lateral rootlets that form a mat in the soil just below the leaf litter. These enhance solubilisation of nutrients, thus allowing nutrient uptake in low-nutrient soils such as the phosphorus-deficient native soils of Australia. Studies on B. integrifolia suggest that its proteoid root mat achieves this by chemically modifying its soil environment. B. integrifolia flowers have an unusually short life span for Banksia species, producing nectar for only about four to twelve days after anthesis. Most nectar is produced during the night and early in the morning, with only small amounts produced during the day. Flowers are produced all through the year, but there is a strong peak in autumn. Little else flowers within its range at this time, so it is a seasonally important source of food for nectariferous animals. …

The wood of B. integrifolia is pink to red, with inconspicuous rings and conspicuous rays. It is spongy and porous, with a density of around 530 kg/m3 (33 lb/cu ft). It is considered highly decorative, but it warps badly on drying, has poor load-bearing qualities, and is susceptible to termite attack; it is therefore unsuitable for most construction purposes. It is sometimes used for cabinet panelling and in ornamental turnery, and natural bends were once sought after for making boat knees. It is a useful firewood. B. integrifolia produces a dark amber-coloured honey of middling quality and therefore low commercial value. Despite this, the species is highly valued by beekeepers because it produces large amounts of pollen and nectar during autumn and winter, thus helping support hives at a time when little else is flowering. Historically, indigenous Australians obtained nectar from B. integrifolia by stroking the flower spikes then licking their hands, or by steeping flower spikes in a coolamon overnight. They also used the flower spikes as hairbrushes. Early settlers used the nectar as a syrup for sore throats and colds; and bushmen would impregnate barren "cones" with fat to make a slow-burning candle. More recently, B. integrifolia has been used in the art of bonsai. …

Hardy and versatile, B. integrifolia will grow in clay, sand, acid and even alkaline soils, and it shows good resistance to wind and salt, making it suitable for seaside planting. It is therefore highly regarded as a low-maintenance garden tree, although its large size makes it unsuitable for smaller gardens. Its hardiness may, however, forewarn weed potential, as some evidence of weediness has been seen in South Africa, Western Australia and New Zealand. When growing near bushland within its native habitat, it is suggested to obtain local provenance plants if available. The most common form available in commercial nurseries is unimproved Banksia integrifolia subsp. integrifolia. It prefers a sunny aspect without exposure to frosts, and tolerates fairly heavy pruning. Seeds do not require any treatment, and take 5 to 6 weeks to germinate. Flowering begins at around four to six years from seed. The other subspecies are less well known in cultivation, but are obtainable. Cultivation is presumably similar to B. integrifolia subsp. integrifolia, except that B. integrifolia subsp. monticola may be assumed frost-tolerant. Dwarf forms of B. integrifolia are sometimes sold, and a registered prostrate cultivar, Banksia 'Roller Coaster', is available. …