Banksia aculeata

Shrub of the family Proteaceae native to the southwest of Western Australia. Banksia aculeata, commonly known as prickly banksia, is a species of plant of the family Proteaceae native to the Stirling Range in the southwest of Western Australia. A shrub up to tall, it has dense foliage and leaves with very prickly serrated margins. Its unusual pinkish, pendent (hanging) flower spikes, known as inflorescences, are generally hidden in the foliage and appear during the early summer. Although it was collected by the naturalist James Drummond in the 1840s, Banksia aculeata was not formally described until 1981, by Alex George in his monograph of the genus. A rare plant, Banksia aculeata is found in gravelly soils in elevated areas. Native to a habitat burnt by periodic bushfires, it is killed by fire and regenerates from seed afterwards. In contrast to other Western Australian banksias, it appears to have some resistance to the soil borne water mould Phytophthora cinnamomi.

A bushy shrub, Banksia aculeata grows up to tall, with fissured grey bark on its trunk and branches. Unlike many other banksia species, it does not have a woody base, or lignotuber. The leaves range from long and wide, with sharply pointed rigid lobes on the margins. Oval in shape, the follicles are wrinkled in texture and covered with fine hair. They are long, high, and wide. George placed B. aculeata in B. subg. Banksia because its inflorescence is a typical Banksia flower spike; in B. sect. Banksia because of its straight styles; and B. ser. Tetragonae because of its pendulous inflorescences. He considered its closest relative to be B. caleyi, from which it differs in having narrower leaves with fewer, larger lobes; longer perianths, which grade from red to cream rather than from cream to red; shorter pistils; and also differences in the follicles, seeds and flowering time. B. aculeatas placement in Thiele and Ladiges' arrangement may be summarised as follows: A 2013 molecular study by Marcel Cardillo and colleagues using chloroplast DNA and combining it with earlier results found that B. aculeata was sister to B. lemanniana and that B. caleyi was the next closest relative. Early in 2007 Mast and Thiele initiated a rearrangement by transferring Dryandra to Banksia, and publishing B. subg. Spathulatae for the species having spoon shaped cotyledons; in this way they also redefined the autonym B. subg. Banksia. They foreshadowed publishing a full arrangement once DNA sampling of Dryandra was complete; in the meantime, if Mast and Thiele's nomenclatural changes are taken as an interim arrangement, then B. aculeata is placed in B. subg. Banksia.

B. aculeata is native to the foothills of the Stirling Range in the southwest of Western Australia, occurring at elevations between , in shrubland in gravelly, clayish soils. With fairly small populations and a narrow distribution, B. aculeata is considered rare, but is not currently classed as endangered because at least some populations are thought not to be under immediate threat. The Department of Environment and Conservation of the Western Australian State Government classes it as "Priority Two – Poorly Known" flora.

Like many plants in Australia's southwest, Banksia aculeata is adapted to an environment in which bushfire events are relatively frequent. Most Banksia species can be placed in one of two broad groups according to their response to fire: reseeders are killed by fire, but fire also triggers the release of their canopy seed bank, thus promoting recruitment of the next generation; resprouters survive fire, resprouting from a lignotuber or, more rarely, epicormic buds protected by thick bark. B. aculeata is killed by fire because it possesses neither thick protective bark nor a lignotuber to reshoot from. It is serotinous—it accumulates a canopy seed bank that is released only in response to fire—so populations typically recover rapidly after a fire, but this strategy makes it dependent on a suitable fire regime. Plants take three to four years to reach flowering after a bushfire. but in a 2008 study this pathogen was found to have no direct impact on the species. As a result of this finding, together with the low percentage of populations infested or facing imminent infestation, the species was classed as having a very low extinction risk.

Banksia aculeata grows slowly, generally taking five to six years to flower from seed, though there is a report of it flowering in three years at Strathmerton in Victoria. Regarding its potential as an ornamental plant, Alex George observes that the flowers are brightly coloured but have a short life and are obscured by the foliage, which is quite prickly. He nonetheless considers both the new foliage and the infructescence attractive. This species can grow in a range of soil types so long as they provide good drainage. The nominal soil pH range is from 5.5 to 6.5. It prefers full sun, although it will grow in partly shaded situations, producing fewer flowers. It will tolerate light pruning.