View source for Banksia prionotes

{{SPlantbox
|familia=Proteaceae
|genus=Banksia
|species=prionotes
|common_name=Acorn Banksia, Orange Banksia
|name_ref=Wikipedia
|Min ht box=15
|Min ht metric=ft
|Max ht box=30
|Max ht metric=ft
|height_ref=Flora - A Gardener's Encyclopedia ISBN 0881925381
|Max wd box=10
|Max wd metric=ft
|width_ref=Flora - A Gardener's Encyclopedia ISBN 0881925381
|lifespan=perennial
|exposure=sun
|sun_ref=Flora - A Gardener's Encyclopedia ISBN 0881925381
|water=moderate, dry
|water_ref=Flora - A Gardener's Encyclopedia ISBN 0881925381
|features=flowers, foliage, cut flowers
|flower_season=early fall, mid fall, late fall, early winter, mid winter, late winter
|flower_ref=Flora - A Gardener's Encyclopedia ISBN 0881925381
|flowers=orange
|Temp Metric=°F
|min_zone=10
|usda_ref=Flora - A Gardener's Encyclopedia ISBN 0881925381
|max_zone=11.5
|image=Banksia prionotes 3 gnangarra.jpg
|image_width=240
}}
'''''Banksia prionotes''''', commonly known as '''Acorn Banksia''' or '''Orange Banksia''', is a species of [[shrub]] or [[tree]] of the genus ''[[Banksia]]'' in the family [[Proteaceae]]. It is native to the [[southwest botanical province|southwest]] of [[Western Australia]] and can reach up to 10&nbsp;m (30&nbsp;ft) in height. It can be much smaller in more exposed areas or in the north of its range. This species has serrated, dull green leaves and large, bright flower spikes, initially white before opening to a bright orange. Its common name arises from the partly opened [[inflorescence]], which is shaped like an [[acorn]]. The tree is a popular garden plant and also of importance to the [[floriculture|cut flower industry]].

''Banksia prionotes'' grows as a tree up to 10&nbsp;m (30&nbsp;ft) high in southern parts of its distribution, but in northern parts it is usually a shorter tree or spreading shrub, reaching about 4&nbsp;m (13&nbsp;ft) in height; it diminishes in size as the climate becomes warmer and dryer further north.<ref name="Cowling 1985">{{cite journal | last1 = Cowling | first1 = R. M. | last2 = Lamont | first2 = B. B. | year = 1985 | title = Variation in serotiny of three ''Banksia'' species along a climatic gradient | journal = Australian Journal of Ecology | volume = 10 | issue = 3 | pages = 345–50 | doi = 10.1111/j.1442-9993.1985.tb00895.x}}</ref> It has thin, mottled grey, smooth or grooved bark, and [[tomentose]] young stems. The [[Leaf#Arrangement on the stem|alternate]] dull green leaves are 15–27&nbsp;cm (6–11&nbsp;in) long, and 1–2&nbsp;cm (⅓–⅔&nbsp;in) wide, with toothed [[leaf margin]]s made up of triangular lobes, and often a wavy surface.<ref name="George 1981">{{cite journal | last1 = George | first1 = Alex S. | year = 1981 | title = [[The genus Banksia L.f. (Proteaceae)|The genus ''Banksia'' L.f. (Proteaceae)]] | journal = [[Nuytsia (journal)|Nuytsia]] | volume = 3 | issue = 3 | pages = 239–473 | id = {{ISSN|0085-4417}}}}</ref><ref name="George 1999">{{cite encyclopedia | last1 = George | first1 = Alex S. | year = 1999 | title = Banksia | editor = Wilson, Annette (ed.) | encyclopedia = [[Flora of Australia (series)|Flora of Australia]] | volume = 17B | pages = 175–251 | location = Collingwood, Victoria | publisher = CSIRO Publishing / Australian Biological Resources Study | isbn = 0-643-06454-0}}</ref>

Flowers occur in a typical ''Banksia'' flower spike, an [[inflorescence]] made up of hundreds of small individual flowers, or florets, densely packed around a cylindrical axis. ''B.&nbsp;prionotes'' has cream-coloured flowers with a bright orange limb that is not revealed until the flower fully opens. Known as [[anthesis]], this process sweeps through the inflorescence from bottom to top over a period of days, creating the effect of a cream inflorescence that progressively turns bright orange. The old flower parts fall away after flowering finishes, revealing the axis, which may bear up to 60 embedded [[follicle (fruit)|follicles]]. Oval or oblong in shape and initially covered in fine hairs, these follicles are from 14 to 20&nbsp;mm (0.55–0.8&nbsp;in) long and 6–11&nbsp;mm (0.25–0.4&nbsp;in) wide, and protrude 3–6&nbsp;mm (0.1–0.25&nbsp;in) from the cone. Inside, they bear two seeds separated by a brownish woody [[seed separator]]. The matte blackish seeds are wedge-shaped (cuneate) and measure 8–10&nbsp;mm (0.3–0.4&nbsp;in) long by 5–6&nbsp;mm (0.2–0.25&nbsp;in) wide with a membranous 'wing'.<ref name="George 1981"/><ref name="George 1999"/>

The root system consists of a main [[sinker root]], and up to ten [[lateral root]]s extending from a non-[[lignotuber]]ous [[root crown]]. The main sinker root grows straight down to the water table; it may be up to 15&nbsp;m (50&nbsp;ft) long if the water table is that deep. Typically from 3 to 5&nbsp;cm (1.4–2&nbsp;in) in diameter immediately below the root crown, roots become gradually finer with depth, and may be less than half a centimetre (0.2&nbsp;in) wide just above the water table. Upon reaching the water table, the sinker branches out into a network of very fine roots. The laterals radiate out horizontally from the base of the plant, at a depth of 3–10&nbsp;cm (2.4–4&nbsp;in). They may extend over 5&nbsp;m (15&nbsp;ft) from the plant, and may bear secondary laterals; larger laterals often bear auxiliary sinker roots. Lateral roots seasonally form secondary rootlets from which grow dense surface mats of [[proteoid root]]s, which function throughout the wetter months before dying off with the onset of summer.<ref name="Jeschke 1995">{{cite journal | last1 = Jeschke | first1 = W. Dieter | last2 = Pate | first2 = John S. | year = 1995 | title = Mineral nutrition and transport in xylem and phloem of ''Banksia prionotes'' (Proteaceae), a tree with dimorphic root morphology | journal = Journal of Experimental Botany | volume = 46 | issue = 289 | pages = 895–905 | doi = 10.1093/jxb/46.8.895}}</ref><ref name="Pate 1995">{{cite journal | last1 = Pate | first1 = John S. | last2 = Jeschke | first2 = W. Dieter | last3 = Aylward | first3 = Matt J. | year = 1995 | title = Hydraulic architecture and xylem structure of the dimorphic root systems of South-West Australian species of Proteaceae | journal = Journal of Experimental Botany | volume = 46 | issue = 289 | pages = 907–15 | doi = 10.1093/jxb/46.8.907}}</ref><ref name="Pate 1999">{{cite journal | last1 = Pate | first1 = John S. | last2 = Bell | first2 = T. L. | year = 1999 | title = Application of the ecosystem mimic concept to the species-rich ''Banksia'' woodlands of Western Australia | journal = Agroforestry Systems | volume = 45 | issue = 1/3 | pages = 303–41 | note = See Section 3. ''Banksia prionotes''—major player of the woodlands | doi = 10.1023/A:1006218310248}}</ref>

Summer-only shoot growth is maintained throughout the life of the plant, except that in mature plants, seasonal shoot growth may cease with the formation of a terminal inflorescence rather than a resting bud.<ref name="Pate 1999"/><ref name="Pate 1998">{{cite journal | last1 = Pate | first1 = John S. | last2 = Jeschke | first2 = Dieter | last3 = Dawson | first3 = Todd E. | last4 = Raphael | first4 = Carlos | last5 = Hartung | first5 = Wolfram | last6 = Bowen | first6 = Barbara J. | year = 1998 | title = Growth and seasonal utilisation of water and nutrients by ''Banksia prionotes'' | journal = Australian Journal of Botany | volume = 46 | issue = 4 | pages = 511–532 | doi = 10.1071/BT97045}}</ref> Inflorescence development continues after shoot growth ceases, and flowering commences in February or March. March and April are the peak months for flowering, which ends in July or August.<ref name="Taylor 1988"/>

Annual growth increases exponentially for the first eight years or so, but then slows down as resources are diverted into reproduction and the greater density of foliage results in reduced [[photosynthesis|photosynthetic]] [[Photosynthetic efficiency|efficiency]].<ref name="Pate 1998"/>