Appearance''Banksia serrata'' usually grows as a gnarled and misshapen tree up to 16 m tall, although in some coastal habitats it grows as a shrub of 1–3 m , and on exposed coastal cliffs it has even been recorded as a prostrate shrub. As a tree it usually has a single, stout trunk with warty, knobbly grey bark up to 3 cm thick. Trunks are often black from past bushfires, and ooze a red sap when injured. New growth appears in spring, summer and autumn. New branchlets are hairy, remaining so for two to three years. Leaves are usually crowded together at the upper end of branches, giving the canopy a thin, sparse appearance. The leaves themselves are dark glossy green above and light green below, 7 to 20 centimetres ) long by 2 to 4 cm ) wide, and oblong to obovate in shape. The leaf margins are serrated, except near the base, with lobes between 1 and 3 millimetres deep.
Cylindrical flower spikes, or inflorescences, grow from the ends of 1–2 year-old branchlets and have leaves at their base. The spikes are generally 9 to 12 centimetres wide with hundreds of individual flowers arising from an upright woody axis. The woody axis is 7 to 15 centimetres high and 0.9 to 1 centimetre wide. The flowers are cream-grey in colour with cream styles. Old flower spikes develop into "cones" that consist of up to thirty follicles that develop from the flowers that were pollinated. Old withered flower parts remain on the cones, giving them a hairy appearance. Each follicle is oval in shape, wrinkled in texture, covered with fine hair and 2.5–3.5 cm long, 2.0–2.5 cm thick, and 1.5–2.2 cm wide.
The obovate seed is 3–3.4 cm long, fairly flattened, has a papery wing and weighs around 77.5 mg . The seed is composed of the obovate seed body and measures 1.0–1.2 cm long by 0.9–1.1 cm wide. One side, termed the outer surface, is pitted and dark brown and the other is brown-black and warty, sparkling slightly. The seeds are separated in the follicle by a sturdy dark brown seed separator, which is about the same shape as the seeds, with a depression where the seed body sits adjacent to it. The first pair of leaves produced by seedlings are obovate, dull green and measure 1–1.4 cm long by 1–1.5 cm wide. The auricle at the base of the cotyledon leaf is pointed and measures 0.2 cm long. The hypocotyl is thick, hairy and red. The cotyledons are linear to lance-shaped with the narrow end towards the base, 3.5–10 cm long with serrated margins and a v-shaped sinus at the tip.
''Banksia serrata'' closely resembles ''B. aemula'', but the latter can be distinguished by an orange-brown, rather than greyish, trunk, and adult leaves narrower than 2 cm in diameter. The inflorescences of ''B. serrata'' are generally a duller grey-yellow in colour, have longer , more fusiform or cylindrical pollen presenters on the tips of unopened flowers and the follicles are smaller.
Naming''B. serrata'' is one of the four original ''Banksia'' species collected by Sir Joseph Banks in 1770, and one of four species published in 1782 as part of Carolus Linnaeus the Younger's original description of the genus. There are no recognised varieties, although it is closely related to ''Banksia aemula''. Throughout its range, it grows exclusively in sandy soils, and is usually the dominant plant in scrubland or low woodland. ''B. serrata'' is pollinated by and provides food for a wide array of vertebrate and invertebrate animals in the autumn and winter months, and is an important source of food for honeyeaters. It is a common plant of parks and gardens.
Distribution''Banksia serrata'' occurs on the Australian mainland from Wilsons Promontory, Victoria in the south, to Maryborough, Queensland in the north. There is also a large population at Sisters Creek in Tasmania and another in the south west corner of the Wingaroo Nature Reserve in the northern part of Flinders Island. The Wingaroo NR Conservation Plan reports that the population comprises around 60 to 80 individual trees, the majority of which are believed to be "quite old". It adds that there is evidence of slow and continuous regeneration, which appears to be occurring in the absence of fire.
Throughout its range, ''Banksia serrata'' is found on well-drained sandy soils that are low in nutrients, and is often found on stabilised soil near the coast but just behind the main dune system. In the Sydney region it is found with other typical woodland species, including yellow bloodwood , red bloodwood , silvertop ash , blue-leaved stringybark and Sydney peppermint .
In the Upper Myall River region, ''B. serrata'' grows in dry sclerophyll forest on sandy soils that have recently formed or in shallow soils over differing substrates, while its close relative ''B. aemula'' grows on dry heath forest that occurs on ancient Pleistocene sands that have not been disturbed in 125,000 years. In intermediate communities both species are found.
''Banksia serrata'' is a component of the Eastern Suburbs Banksia Scrub , designated an endangered ecological community. This community is found on windblown sands which are younger than the heathlands to the north.
CulturalThe gnarled lumpy bark, saw-toothed leaves and silvery-yellow spikes in bud are horticultural features of ''B. serrata''. It can be grown readily from seed, collected after heating the "cone". A sterile, free-draining seed-raising mixture prevents damping off. In cultivation, though relatively resistant to ''P. cinnamomi'' dieback, it grows best in a well drained soil, preferably fairly sandy with a pH from 5.5 to 7.5, and a sunny aspect. Summer watering aids in growth. The plant may take several years to flower, although plants grown from cuttings may flower in two years. ''Banksia serrata'' is also used in bonsai.
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