Banksia Media

''Banksia media'', the southern plains banksia or golden stalk banksia, is a species of flowering plant in the family Proteaceae. An evergreen shrub, it occurs on the south coast of Western Australia between Albany and Israelite Bay, where it is a common plant. A many-branched bush with wedge-shaped serrated leaves and large golden-yellow flower spikes, known as inflorescences, it grows up to 10 metres (30 ft) high.

These plants are killed by bushfire, and regenerate from seed. The flowers attract nectar- and insect-feeding birds, particularly honeyeaters, and a variety of insects. In cultivation, ''Banksia media'' grows well in a sunny location on well-drained soil in areas with dry summers. It is more resilient than most Western Australian banksias when cultivated in areas with humid summers.

Description

''Banksia media'' grows as a many-stemmed shrub generally to around 4 m (13 ft) high, though specimens up to 10 m (30 ft) high and 6 m (20 ft) wide have been recorded. The trunk can reach 30 cm (12 in) in diameter. Conversely, some coastal populations such as at Point Ann have plants with a prostrate habit with the flower spikes towering above the foliage. Unlike many banksias, it does not have a lignotuber. It has grey, fissured bark, and hairy stems, putting on new growth in summer. Alternately arranged along the stems, the dark green, wedge-shaped leaves are 4 to 12 cm (1.8–4.2 in) long and 0.7 to 2 cm (0.3–0.8 in) wide with serrated margins. Leaf dimensions vary in different populations: plants from the western and coastal parts of its range have shorter and broader leaves—4 to 6 cm by 1 to 2 cm, while inland plants from around Mt Charles and Mt Ragged have longer and narrower leaves and less revolute leaf margins.

Flowering takes place mainly from March to August, though occasional flower spikes may appear till December. The cylindrical spikes arise on the ends of short lateral branchlets off three- or five-year-old stems and are generally 6 to 16 cm high and 7 to 8 cm (~3 in) wide at anthesis. One population at Mt Ridley has spikes often reaching 26 cm high. Known as an inflorescence, each is a compound flowering structure, with a large number of individual flowers arising out of a central woody axis.

Taxonomy

Robert Brown described ''Banksia media'' in his 1830 supplement to his ''Prodromus Florae Novae Hollandiae et Insulae Van Diemen'', the type specimen having been collected between Cape Arid and Lucky Bay by collector William Baxter in 1824.

George Bentham published a thorough revision of ''Banksia'' in his landmark publication ''Flora Australiensis'' in 1870. In Bentham's arrangement, the number of recognised ''Banksia'' species was reduced from 60 to 46. Bentham defined four sections based on leaf, style and pollen-presenter characters. ''Banksia media'' was placed in section ''Cyrtostylis''.

In 1891, Otto Kuntze, in his ''Revisio Generum Plantarum'', rejected the generic name ''Banksia'' L.f., on the grounds that the name ''Banksia'' had previously been published in 1776 as ''Banksia'' J.R.Forst & G.Forst, referring to the genus now known as ''Pimelea''. Kuntze proposed ''Sirmuellera'' as an alternative, referring to this species as ''Sirmuellera media''. This application of the principle of priority was largely ignored by Kuntze's contemporaries, and ''Banksia'' L.f. was formally conserved and ''Sirmuellera'' rejected in 1940.

Infrageneric placement

George placed ''B. media'' in ''B.'' subg. ''Banksia'', because its inflorescences are typical ''Banksia'' flower spikes; ''B.'' sect. ''Banksia'' because of its straight styles; and ''B.'' ser. ''Cyrtostylis'' because it has slender flowers. He considered its closest relatives to be '' B. praemorsa'' (cut-leaf banksia) and, after its discovery, ''B. epica''.

In 1996, Kevin Thiele and Pauline Ladiges published the results of a cladistic analysis of morphological characters of ''Banksia''. They retained George's subgenera and many of his series, but discarded his sections. George's ''B.'' ser. ''Cyrtostylis'' was found to be "widely polyphyletic", as six of the fourteen taxa in that series occurred singly in locations throughout Thiele and Ladiges' cladogram. The remaining eight formed a clade that further resolved into two subclades, with ''B. media'' appeared in one of them, alongside ''praemorsa'', ''epica'' and ''pilostylis'':

Since 1998, Austin Mast has been publishing results of ongoing cladistic analyses of DNA sequence data for the subtribe Banksiinae. His analyses suggest a phylogeny that is rather different from previous taxonomic arrangements. With respect to ''B. media'', however, Mast's results accord closely with the arrangement of Thiele and Ladiges, placing it in a polytomous clade corresponding exactly with Thiele and Ladiges' ''B.'' ser. ''Cyrtostylis''.

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. media'' is placed in ''B.'' subg. ''Banksia''.

Distribution and habitat

''Banksia media'' is widely distributed across southern Western Australia, from the eastern border of Stirling Range National Park across to Israelite Bay and extending northwards to Pingrup, Frank Hann National Park, 15 km east northeast of Dowak and 35 km northwest of Mt Buraminya. A disjunct population occurs further east along the coast at Point Culver and Toolinna. Often locally abundant, it grows in a variety of soil types, most commonly white sand or a sandy loam, but also red clay, loam over limestone, shale or granitic soil. The habitat is heathland, shrubland or open woodland.

Ecology

''Banksia media'' is killed by bushfire and regenerates from seed. Plants in the Fitzgerald River National Park take around ten years to flower and set seed after germination, where fires are generally 30 to 60 years apart.

The prominent and colourful flower spikes indicate they are attractive to vertebrate pollinators, and they are visited by a variety of species, including honey possums and a number of honeyeaters, including the New Holland honeyeater, white-cheeked honeyeater, red wattlebird and western spinebill. Insects include the meat ant and European honeybee. A field study excluding pollinators showed that the spikes can set fruit without pollinators, indicating they have a degree of self-compatibility.

Cultivation

''Banksia media'' has been shown to have a relatively low susceptibility to dieback from the soil-borne water mould ''Phytophthora cinnamomi'', unlike many Western Australian banksias.
Seeds do not require any treatment, and take 20 to 46 days to germinate.

References

External links

*

{{Taxonbar, from=Q2712431

media
Eudicots of Western Australia
Endemic flora of Western Australia
Taxa named by Robert Brown (botanist, born 1773)
Plants described in 1830