Banksia spinulosa, the hairpin banksia, is a species of woody shrub, of the genus Banksia in the family Proteaceae, native to eastern Australia. Widely distributed, it is found as an understorey plant in open dry forest or heathland from Victoria to northern Queensland, generally on sandstone though sometimes also clay soils. It generally grows as a small shrub to in height, though can be a straggly tree to . It has long narrow leaves with inflorescences which can vary considerably in coloration; while the spikes are gold or less commonly yellowish, the emergent styles may be a wide range of colours – from black, purple, red, orange or yellow.
Banksia spinulosa was named by James Edward Smith in England in 1793, after being collected by John White, most likely in 1792. He gave it the common name prickly-leaved banksia, though this has fallen out of use. With four currently recognised varieties, the species has had a complicated taxonomic history, with two varieties initially described as separate species in the early 19th century. A fourth, from the New England region, has only recently been described. However, there has been disagreement whether one, var. cunninghamii, is distinct enough to once again have specific status. The pre-eminent authority on Banksia, Alex George, concedes there is still more work to be done on the Banksia spinulosa complex.
The hairpin banksia is pollinated by and provides food for a wide array of vertebrate and invertebrate animals in the autumn and winter months. Its floral display and fine foliage have made it a popular garden plant with many horticultural selections available. With the recent trend towards smaller gardens, compact dwarf forms of Banksia spinulosa have become popular; the first available, Banksia 'Birthday Candles', has achieved a great deal of commercial success and wide recognition, and has been followed by several others.
Description The hairpin banksia usually occurs as a multi-stemmed lignotuberous shrub tall and across. Alternatively, it may be single-stemmed and lacking a lignotuber, in which case it is often taller, up to high. It has grey or grey-brown smooth bark with lenticels. The long, narrow leaves are in length, 1–8 mm wide and more or less linear in shape. Leaf edges are either serrate for the entire leaf length (collina) or toward the apex only (spinulosa), though the margins may be recurved and hence serrations not evident as in those from the Carnarvon Gorge. Immature leaves, which may also be seen after bushfire, are broader and serrated. Leaf undersides have fine white hairs in the case of the varieties spinulosa and collina and pale brown in cunninghamii and neoanglica.
The distinctive inflorescences or flower spikes occur over a short period through autumn and early winter. A spike may contain hundreds or thousands of individual flowers, each of which consists of a tubular perianth made up of four united tepals, and one long wiry style. Characteristic of the taxonomic section in which it is placed, the styles are hooked rather than straight. The style ends are initially trapped inside the upper perianth parts, but break free at anthesis. In Banksia spinulosa the spikes are cylindrical, about wide and tall, yellow to golden orange in colour, with styles varying from yellow to pink, maroon, or black. Styles of various colours may be found within metres of each other in some areas such as in the Georges River National Park, and Catherine Hill Bay, while other populations may have uniformly black, red or gold styles. Though not terminal, the flower spikes are fairly prominently displayed. Partly emerging from the foliage, they arise from two- to three-year-old stem nodes.
The hairpin banksia's infructescence is a typical Banksia cone-like structure, with up to 100 crowded embedded follicles which are in diameter; these generally remain closed until burnt by bushfire. The nonlignotuberous subspecies cunninghamii is killed by fire and regenerates from seed, while the others regenerate from buds around the base of the lignotuber. Old flower spikes fade to brown, then grey with age. Old flower parts usually persist for a long time, giving the infructescence a hairy appearance. In Central and North Queensland, old cones of both var. spinulosa and var. collina are generally bare.
Taxonomy
The first known specimens of B. spinulosa were collected near Sydney by John White, Surgeon General to the British colony of New South Wales, sometime between 1788 and 1793. He called it "prickly-leaved banksia", though this name has fallen out of use. It is uncertain exactly when he first collected the species; it may have been before 1790, as there is speculation that a sketch in his 1790 Journal of a Voyage to New South Wales is of a B. spinulosa infructescence. Text accompanying the figure states:
English botanist James Edward Smith later tentatively attributed this figure to B. spinulosa:
More recently, however, Alf Salkin has argued that:
White probably collected the type material of B. spinulosa in 1792. The following year, the species was formally described by Smith in his A Specimen of the Botany of New Holland. It was thus the seventh Banksia species collected, and the fifth described. Smith gave it the specific epithet spinulosa, a Latin term meaning having minute spines, probably in reference to the leaf tips. Thus the species' full name is Banksia spinulosa Sm.
Placement within Banksia In the first infrageneric arrangement of Banksia, that of Brown in 1830, B. spinulosa was placed in subgenus Banksia verae, the "true banksias", because its inflorescence is a typical Banksia flower spike. It was placed next to B. cunninghamii and B. collina, both now considered varieties of B. spinulosa; these three were placed between B. ericifolia (heath-leaved banksia) and B. occidentalis (red swamp banksia). Banksia verae was renamed Eubanksia by Stephan Endlicher in 1847. Carl Meissner demoted Eubanksia to sectional rank in his 1856 classification, and divided it into four series, with B. spinulosa placed in series Abietinae, while B. cunninghamii and B. collina were placed alongside each other in series Salicinae. When George Bentham published his 1870 arrangement in Flora Australiensis, he discarded Meissner's series, placing all the species with hooked styles together in a section that he named Oncostylis. B. cunninghamii was reduced to synonymy with B. collina, as was the western species B. littoralis (western swamp banksia). This arrangement would stand for over a century.
Alex George published a new taxonomic arrangement of Banksia in his landmark 1981 monograph The genus Banksia L.f. (Proteaceae). Endlicher's Eubanksia became B. subg. Banksia, and was divided into three sections, one of which was Oncostylis. Oncostylis was further divided into four series, with B. spinulosa placed in series Spicigerae because its inflorescences are cylindrical.
In 1996, Kevin Thiele and Pauline Ladiges published a new arrangement for the genus, after cladistic analyses yielded a cladogram significantly different from George's arrangement. Thiele and Ladiges' arrangement retained B. spinulosa in series Spicigerae, placing it alone in B. subser. Spinulosae. This arrangement stood until 1999, when George effectively reverted to his 1981 arrangement in his monograph for the Flora of Australia series.
Under George's taxonomic arrangement of Banksia, B. spinulosas taxonomic placement may be summarised as follows: Genus Banksia Subgenus Banksia Section Banksia Section Coccinea Section Oncostylis Series Spicigerae B. spinulosa B. spinulosa var. spinulosa B. spinulosa var. collina B. spinulosa var. neoanglica B. spinulosa var. cunninghamii B. ericifolia B. verticillata B. seminuda B. littoralis B. occidentalis B. brownii Series Tricuspidae Series Dryandroidae Series Abietinae Subgenus Isostylis
More recent molecular research suggests that B. spinulosa and B. ericifolia may be more closely related to series Salicinae, with Banksia integrifolia and its relatives.
In 2005, Austin Mast, Eric Jones and Shawn Havery published the results of their cladistic analyses of DNA sequence data for Banksia. They inferred a phylogeny very greatly different from the accepted taxonomic arrangement, including finding Banksia to be paraphyletic with respect to Dryandra. A new taxonomic arrangement was not published at the time, but 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. 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. spinulosa is placed in B. subg. Spathulatae.
Varieties
Four varieties are currently recognised: B. spinulosa var. spinulosa The nominate race is an autonym, a name that was automatically created for the original material of the species as the other subspecies were described. The original hairpin banksia, this plant is coastal in Queensland, seen in such places as Walshs Pyramid (near Cairns), Byfield National Park and the Blackdown Tableland, then again in New South Wales south of the Hawkesbury River, just north of Sydney, down the New South Wales South Coast and into Victoria. Northwards of the Hawkesbury River on Sydney's northern outskirts there is a gradation between this and B. spinulosa var. collina. It commonly has black, maroon or claret styles on gold spikes but all-gold inflorescences are seen, and leaves are generally narrower than other varieties at 1–2 mm in width and have several serrations toward the apex only.
B. spinulosa var. collina Known as the hill banksia, it was first published as Banksia collina by Robert Brown in 1810, and retained species rank until 1981, when George demoted it to a variety of B. spinulosa. It differs from B. spinulosa var. spinulosa in having broader leaves 3–8 mm in width that have serrate margins. The leaf undersides have more prominent venation. Its flower spikes are usually gold, or sometimes gold with red styles, especially in New South Wales. It is found in inland gorges and tablelands such as Carnarvon Gorge, Expedition National Park, Isla Gorge and Dicks Tableland in a remote part of Eungella National Park, in Central Queensland but coastal on the New South Wales Central- and north coast.
B. spinulosa var. cunninghamii This variety was published as B. cunninghamii in 1827 in honour of the botanist Allan Cunningham, and demoted to a variety of B. spinulosa in 1981. The demotion has not been universally accepted however: in New South Wales it is still given species rank, and B. spinulosa var. neoanglica is considered a subspecies of it. George notes that at locations where both var. spinulosa and var. cunninghamii coexist, such as Fitzroy Falls in Lawson, no intermediate forms occur. This plant is a fast-growing nonlignotuberous shrub or small tree to in height, occurring in the Great Dividing Range from southeast Queensland to southern New South Wales and also in Victoria. The juvenile leaves are highly serrated, new branchlets are hairy and leaf undersides are pale brown rather than white as in the two previous varieties. Inflorescences are gold with black styles, though an all-yellow form from Victoria is known. The linear to oblanceolate adult leaves are long by 2–7 mm wide; those from Victoria having markedly longer juvenile leaves, and larger cotyledons.