Banksia attenuata

It has long, narrow, serrated leaves and bright yellow inflorescences, or flower spikes, held above the foliage, which appear in spring and summer.

It has been widely used as a street tree and for amenities planting in urban Western Australia, though its large size generally precludes use in small gardens.

Tree forms have a solid trunk, generally wavy or bent, with 1–2 cm (0.4–0.8 in) thick crumbly orange-grey bark which is a red-brown underneath.

[10] Often bright green in bud stage,[11] they are terminal, occurring at the ends of one- to three-year-old branches, and displayed prominently above the foliage.

[5] However, only a very small percentage (0.1%) of flowers develop into follicles; the field study at Mount Adams yielded a count of 3.6 ± 1.2 per cone.

[5] In 1840, John Lindley published a putative new species, Banksia cylindrostachya, in his A Sketch of the Vegetation of the Swan River Colony; this has now been shown to be a taxonomic synonym of B. attenuata.

[15] This application of the principle of priority was largely ignored by Kuntze's contemporaries,[16] and Banksia L.f. was formally conserved and Sirmuellera rejected in 1940.

The placement of B. attenuata in George's 1999 arrangement may be summarised as follows:[7] Since 1998, American botanist Austin Mast and co-authors have been publishing results of ongoing cladistic analyses of DNA sequence data for the subtribe Banksiinae, which then comprised genera Banksia and Dryandra.

Banksia attenuata resolves as a basal member of and next closest relative, or 'sister', to a clade containing B. elegans and, within that, a monophyletic B. subg.

[8] Within open woodland, it is found alongside B. menziesii, B. ilicifolia, B. prionotes, Allocasuarina fraseriana, Eucalyptus marginata, or E. gomphocephala.

[11] Like many plants in southwest Western Australia, B. attenuata is adapted to an environment in which bushfire events are relatively frequent.

[27] An experiment simulating wet weather following a fire saw a series of Banksia attenuata cones with follicles subjected to twice-weekly immersions in water after being heated in a ring Bunsen flame to around 500–600 °C (932–1,112 °F) for two minutes.

[28] Once released, seed germinates at temperatures between 15 and 20 °C (59–68 °F) to optimise timing with autumn and winter rains and hence maximise chance of survival.

A genetic study of populations in Eneabba showed that over 5% of plants had originated up to 2.6 km (1.6 mi) away (similar rates to Banksia hookeriana, the seed of which only weighs half as much).

[36] At a site near Jandakot, short-billed black cockatoos were observed selecting immature infructescences which bore signs of infestation by the weevil Alphitopis nivea, the larvae of which tunnel in banksia spikes and eat the seed.

[37] A 1978 field study conducted around Albany found the honey possum (Tarsipes rostratus) was a major pollinator of Banksia attenuata, both feeding directly on the pollen and drinking the nectar.

The flower structure is suited to passing pollen onto the possum as it feeds, unlike honeyeaters whose bills are too long for this to occur readily.

Coupled with the flower spike's musky odour, these findings suggest Banksia attenuata is highly adapted to be pollinated primarily by this mammal species.

[38] Furthermore, Petroc Sumner and colleagues have investigated the cone photoreceptor cells of honey possums and compared them with the colour changes of B. attenuata.

They found that the possum is trichromatic (like humans and possibly many marsupials) and propose that its L (long wavelength) cones help it discern B. attenuata flower spikes, and the M (or medium wavelength) cones could help it distinguish ripe inflorescences with nectar from recently finished spikes (a difficult task for human vision).

[39] There is some evidence for other mammals as pollinators; B. attenuata-like pollen was recovered from museum skins of dunnarts (Sminthopsis spp.)

[40] All banksias have developed proteoid or cluster roots in response to the nutrient-poor conditions of Australian soils (particularly lacking in phosphorus).

[43] Another study on root architecture of Banksia hookeriana, B. menziesii and B. attenuata found the overall structure of all three to be similar, with proteoid mats more active and growing in wetter months (winter-spring).

The two species are less strictly tied to the water table and hence able to grow in a wider variety of places within Banksia woodland habitat around Perth than the co-occurring B. ilicifolia and B. littoralis.

[45] A study at a rehabilitation site on a sand mine north of Perth found that the broadleaved species B. attenuata and B. hookeriana were harder to establish than the fine-leaved B. leptophylla there, due to increased impedance of the disturbed soil.

The symptoms of infection in Banksia attenuata include yellowing of the leaves in the tree crown, and lesions at the base of the trunk.

[51] Injecting a solution of phosphite into the trunks of affected B. attenuata trees at a disease front in Banksia woodland can delay morbidity from dieback for five years.

[53] A 2003 study found that drenching the soil with 0.50 mM benzoic acid significantly reduced the size of P. cinnamomi lesions.

[56] All forms of Banksia attenuata require good drainage, sandy soil and a sunny position to do well, with a pH between 5.5 and 7.0.

[56] Aboriginal people, particularly the Nyoongar and Yamatji, placed the flower spike in a paperbark-lined hole filled with water to make a sweet drink.

A large tree with a wavy curved pale grey trunk in a dry scrubland type landscape
A large tree in Bold Park , Perth. The trunk is characteristically wavy or bent.
A narrow cylindrical dark spike with many yellowish buds forming along its length
A flower spike in early bud stage
A broader yellow cylindrical flower spike with a clear border halfway up it
An inflorescence halfway through anthesis as the flowers open upwards up the spike
Two greyish old flower spikes with oval valved seed pods
The ageing flowers remain curled against the spike, as the furry follicles develop.
An irregularly shaped bush with many long leaves sprouting from the trunk along its length
A tree with new growth resprouting from epicormic buds after fire
A yellow cylindrical flower spike with ants crawling among the flowers
Ants visit a flower spike part way through anthesis . Note that the lower flowers have opened, and the upper ones are still closed.
A cylindrical flower spike nestled among green narrow leaves
A young plant with several flower spikes rises prominently above the foliage. They are in different stages of development from bud through to maturity.
Dwarf form in cultivation; Margaret River