View source for Banksia

{{SPlantbox
|familia=Proteaceae
|genus=Banksia
|common_name=Banksia
|habit=shrub
|habit_ref=Flora - A Gardener's Encyclopedia ISBN 0881925381
|origin=Australia
|origin_ref=Flora - A Gardener's Encyclopedia ISBN 0881925381
|lifespan=perennial
|life_ref=Flora - A Gardener's Encyclopedia ISBN 0881925381
|exposure=sun
|sun_ref=Flora - A Gardener's Encyclopedia ISBN 0881925381
|water=moderate, dry
|water_ref=Flora - A Gardener's Encyclopedia ISBN 0881925381
|Temp Metric=°F
|image=Banksia prionotes 1 gnangarra.jpg
|image_width=240
|image_caption=Banksia prionotes
}}
'''''Banksia''''' is a [[genus]] of around 170 [[species]] in the [[plant]] [[family (biology)|family]] [[Proteaceae]]. These [[Australia]]n [[wildflower]]s and popular [[Ornamental plant|garden plant]]s are easily recognised by their characteristic flower spikes and fruiting "cones" and heads. When it comes to size, banksias range from prostrate woody [[shrub]]s to trees up to 30 metres tall. They are generally found in a wide variety of landscapes; [[sclerophyll]] forest, (occasionally) rainforest, shrubland, and some more arid landscapes, though not in Australia's deserts.  They are of economic importance to Australia's [[nursery (horticulture)|nursery]] and [[floristry|cut flower]] industries.

''Banksias'' grow as [[tree]]s or woody [[shrubs]].  Trees of the largest species, ''[[Banksia integrifolia|B.&nbsp;integrifolia]]'' (Coast Banksia) and ''[[Banksia seminuda|B.&nbsp;seminuda]]'' (River Banksia), often grow over 15 metres tall, some even grow to standing 30 metres tall.<ref>{{cite journal | author = Liber C | year = 2004 | title = Really Big Banksias | journal = Banksia Study Group Newsletter| volume = 6 | pages = 4–5}}</ref> ''Banksia'' species that grow as shrubs are usually erect, but there are several species that are prostrate, with branches that grow on or below the soil.

The leaves of ''Banksia'' vary greatly between species.  Sizes vary from the narrow, 1–1½ centimetre long leaves of ''[[Banksia ericifolia|B.&nbsp;ericifolia]]'' (Heath-leaved Banksia), to the very large leaves of ''[[Banksia grandis|B.&nbsp;grandis]]'' (Bull Banksia), which may be up to 45 centimetres long.  The leaves of most species have serrated edges, but a few, such as ''B.&nbsp;integrifolia'', do not.  Leaves are usually arranged along the branches in irregular spirals, but in some species they are crowded together in [[Whorl (botany)|whorls]]. Many species have differing juvenile and adult leaves (e.g. ''Banksia integrifolia'' has large serrated juvenile leaves).

The character most commonly associated with ''Banksia'' is the flower spike, an elongated [[inflorescence]] consisting of a woody axis covered in tightly-packed pairs of flowers attached at right angles. A single flower spike generally contains hundreds or even thousands of flowers; the most recorded is around 6000 on inflorescences of ''[[Banksia grandis|B.&nbsp;grandis]]''. Not all ''Banksia'' have an elongate flower spike, however: the members of the small ''[[Banksia subg. Isostylis|Isostylis]]'' complex have long been recognised as ''Banksia''s in which the flower spike has been reduced to a head; and recently the large genus ''Dryandra'' has been found to have arisen from within the ranks of ''Banksia'', and sunk into it as [[Banksia ser. Dryandra|''B.''&nbsp;ser. ''Dryandra'']]. Thus fewer than half of the currently accepted ''Banksia'' taxa possess the elongated flower spike long considered characteristic of the genus.

[[File:Banksia marginata immature and mature.jpg|thumb|''[[Banksia marginata|B.&nbsp;marginata]]'' flower spike before and after [[anthesis]]]]
''Banksia'' flowers are usually a shade of [[yellow]], but [[Orange (colour)|orange]], [[red]], [[pink]] and even [[violet (color)|violet]] flowers also occur.  The colour of the flowers is determined by the colour of the [[perianth]] parts and often the [[carpel|style]].  The style is much longer than the perianth, and is initially trapped by the upper perianth parts.  These are gradually released over a period of days, either from top to bottom or from bottom to top.  When the styles and perianth parts are different colours, the visual effect is of a colour change sweeping along the spike. This can be most spectacular in ''[[Banksia prionotes|B.&nbsp;prionotes]]'' (Acorn Banksia) and related species, as the white inflorescence in bud becomes a brilliant orange. In most cases, the individual flowers are tall, thin saccate (sack-shaped) in shape.

[[File:Banksia Marginata Seed.jpg|thumb|left|[[Seed separator]] of a Silver Banksia (''[[Banksia marginata]]'') with winged seeds still cohering]]
Occasionally, multiple flower spikes can form. This is most often seen in ''[[Banksia marginata]]'' and ''[[Banksia ericifolia|B. ericifolia]]''<ref>{{cite journal |last=Johnson |first=S |year=1992 |title=Multiple Flower Heads |journal=Banksia Study Report |volume=9 |pages=58 |id=ISSN 0728–2893}}</ref><ref>{{cite journal |last=Blake |first=T |year=1988 |title=Multiple Heads |journal=Banksia Study Report |volume=8 |pages=2 |id=ISSN 0728-2893}}</ref> ''(pictured right)''. 

[[File:Banksia integrifolia and marginata cones.jpg|thumb|Infructescence of ''[[Banksia integrifolia|B.&nbsp;integrifolia]]'', with non-persistent flowers; and ''[[Banksia marginata|B.&nbsp;marginata]]'', with persistent flowers]]
As the flower spikes or heads age, the flower parts dry up and may turn shades of orange, tan or dark brown colour, before fading to grey over a period of years.  In some species, old flower parts are lost, revealing the axis; in others, the old flower parts may persist for many years, giving the fruiting structure a hairy appearance.  Old flower spikes are commonly referred to as "cones", although they are not: [[Conifer cone|cones]] only occur in [[conifer]]s and [[cycad]]s.

Despite the large number of flowers per inflorescence, only a few of them ever develop fruit, and in some species a flower spike will set no fruit at all.  The fruit of ''Banksia'' is a woody [[Follicle (fruit)|follicle]] embedded in the axis of the inflorescence.  These consist of two horizontal valves that tightly enclose the seeds.  The follicle opens to release the seed by splitting along the suture, and in some species each valve splits too.  In some species the follicles open as soon as the seed is mature, but in most species most follicles open only after stimulated to do so by [[bushfire]].  Each follicle usually contains one or two small seeds, each with a wedge-shaped papery wing that causes it to spin as it falls to the ground.

[[Image:Banksia prionotes response to fire Burma Rd email.jpg|left|thumb|200px|''[[Banksia prionotes]]'' seedlings after fire, [[Burma Road Nature Reserve]], WA]]
''Banksia'' plants are naturally adapted to the presence of regular [[bushfire]]s in the Australian landscape. About half of ''Banksia'' species are killed by bushfire, but these regenerate quickly from seed, as fire also stimulates the opening of seed-bearing follicles and the germination of seed in the ground.  The remaining species usually survive bushfire, either because they have very thick bark that protects the trunk from fire, or because they have [[lignotuber]]s from which they can resprout after fire. In [[Western Australia]], banksias of the first group are known as 'seeders' and the second group as 'sprouters'.
[[Image:Banksia attenuata response to fire Burma Rd email.jpg|thumb|200px|''[[Banksia attenuata]]'' resprouting after fire, Burma Road Nature Reserve, WA]]

Most of species are shrubs, only few of them can be found as trees and they are very popular because of their size, the tallest species are: ''[[Banksia integrifolia|B.&nbsp;integrifolia]]''  having its subspecies [[Banksia integrifolia subsp. monticola|''B.&nbsp;integrifolia'' subsp. ''monticola'']] notable for reaching the biggest banksias and it is the most frost tolerant in this genus, ''[[Banksia seminuda|B.&nbsp;seminuda]]'', ''[[Banksia littoralis|B.&nbsp;littoralis]]'', ''[[Banksia serrata|B.&nbsp;serrata]]''; species that can grow as small trees or big shrubs: ''[[Banksia grandis|B.&nbsp;grandis]]'', ''[[Banksia prionotes|B.&nbsp;prionotes]]'', ''[[Banksia marginata|B.&nbsp;marginata]]'', ''[[Banksia coccinea|B.&nbsp;coccinea]]'', ''[[Banksia speciosa|B.&nbsp;speciosa]]'' and ''[[Banksia menziesii|B.&nbsp;menziesii]]''. Due to their size these species are popularly planted in parks, gardens and streets, the remaining species in this genus are only shrubs.

''Banksia''s are popular garden plants in Australia because of their large, showy flower heads, and because the large amounts of [[nectar]] they produce attracts [[birds]] and small [[mammal]]s.  Popular garden species include ''B.&nbsp;spinulosa'', ''B.&nbsp;ericifolia'', [[Banksia aemula|''B.&nbsp;aemula'']] (Wallum Banksia ), [[Banksia serrata|''B.&nbsp;serrata'']] (Saw Banksia), ''[[Banksia media]]'' (Southern Plains Banksia) and the [[cultivar]] [[Banksia 'Giant Candles'|''Banksia'' 'Giant Candles']].  ''Banksia'' species are primarily propagated by seed in the home garden as cuttings can be difficult to strike. However commercial nurserymen extensively utilize the latter method (indeed, cultivars by nature must be vegetatively propagated by cuttings or grafting).

Over time, dwarf cultivars and prostrate species are becoming more popular as urban gardens grow ever smaller. These include miniature forms under 50&nbsp;cm high of ''B.&nbsp;spinulosa'' and ''B.&nbsp;media'', as well as prostrate species such as ''[[Banksia petiolaris|B.&nbsp;petiolaris]]'' and ''[[Banksia blechnifolia|B.&nbsp;blechnifolia]]'' .

Banksias possibly require more TLC (i.e. maintenance) than other Australian natives, though are fairly hardy if the right conditions are provided (sunny aspect and well drained sandy soil). 
They may need extra water during dry spells until established, which can take up to two years.  If fertilised, only slow-release, low-[[phosphorus]] [[fertilizer]] should be used, as the [[proteoid roots]] may be damaged by high [[nutrient]] levels in the soil. All respond well to some form of pruning.

Within the Australian horticultural community there is an active subculture of ''Banksia'' enthusiasts who seek out interesting flower variants, breed and propagate cultivars, exchange materials and undertake research into cultivation problems and challenges. The main forum for exchange of information within this group is [[ASGAP]]'s ''Banksia Study Group''.