Hairpin Banksia

The hairpin banksia usually occurs as a multi-stemmed lignotuberous shrub 1–3 metres (3.3–9.8 ft) tall and 1–2 metres (3.3–6.6 ft) across. Alternatively, it may be single-stemmed and lacking a lignotuber, in which case it is often taller, up to 5 metres (16 feet) high. It has grey or grey-brown smooth bark with lenticels. The long, narrow leaves are 3–10 cm (1.2–3.9 in) 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. …

The hairpin banksia occurs along the east coast of Australia from the Dandenong Ranges east of Melbourne, Victoria, north through New South Wales and into Queensland. It is common north to Maryborough, with disjunct populations occurring as far north as the Atherton Tableland near Cairns. It occurs in a variety of habitats, from coastal heath (spinulosa and collina) and elevated rocky slopes (neoanglica and spinulosa) to inland dry sclerophyll forest dominated by eucalypts, where they form part of the understorey. Plants in exposed areas are generally considerably shorter than those in sheltered areas. It usually occurs on sand, but can be found in rocky clays or loams. Banksia spinulosa var. cunninghamii is found in three disjunct regions; the Dandenong Ranges east of Melbourne, East Gippsland between Lakes Entrance and Eden, and in the Great Dividing Range in a band from Jervis Bay to Glen Davis in Central New South Wales, while there have been collections northwards in the Dividing Range up into southeast Queensland. It can be an understorey plant under dense as well as open forest cover.

Like other banksias, Banksia spinulosa plays host to a wide variety of pollinators and is a vital source of nectar in autumn, when other flowers are scarce. Banksias have been the subject of many studies about their pollination; B. spinulosa is no exception. A 1998 study in Bungawalbin National Park in Northern New South Wales found that B. spinulosa var. collina inflorescences are foraged by a variety of small mammals, including marsupials such as Antechinus flavipes (yellow-footed antechinus), which carry pollen loads comparable to those of nectar-eating birds, making them effective pollinators. The same study noted that, unlike other banksias studied, B. spinulosa var. collina was visited predominantly by native bees rather than the introduced Apis mellifera (European honeybee). A great many bird species have been observed visiting this species. A 1982 study in the New England National Park in northeastern New South Wales found that a large influx of Acanthorhynchus tenuirostris (eastern spinebill) coincided with the start of local B. spinulosa's flowering. In the Blackdown Tableland, Lichenostomus leucotis (white-eared honeyeater) and Lichenostomus melanops (yellow-tufted honeyeater) as well as pygmy possums visit B. spinulosa. Brown antechinus, sugar glider, and bush rat are also known to visit flowers. …

Banksia spinulosa var. spinulosa was introduced into cultivation in the United Kingdom in 1788 by Joseph Banks who supplied seed to Kew, Cambridge Botanic Gardens and Woburn Abbey among others; var. collina followed in 1800 and var. cunninghamii in 1822. It has proven a highly ornamental and bird-attracting plant in cultivation. Southern and montane provenance forms are frost hardy. In general, all forms prefer sandy, well-drained soils with sunny aspect, though some local forms hailing from Wianamatta shales may tolerate heavier soils. It is resistant to dieback, like most eastern banksias. As it grows naturally on acid soils, Banksia spinulosa is particularly sensitive to iron deficiency. Known as chlorosis, it manifests as yellowing of new leaves with preservation of green veins, and occurs when the plant is grown in soils of higher pH. This can also happen where soil contains quantities of cement, either as landfill or building foundations, and can be treated with iron chelate or sulfate. Regular pruning is important to give the plant an attractive habit and prevent it from becoming leggy. As most cultivated forms of this species have a lignotuber, dormant buds exist below the bark that respond to pruning or fire, and hard-pruning is possible almost to ground level as a plant can readily sprout from old wood. This is not the case for var. …