Banksia Prionotes - Description

Description

Banksia prionotes grows as a tree up to 10 m (30 ft) high in southern parts of its distribution, but in northern parts it is usually a shorter tree or spreading shrub, reaching about 4 m (13 ft) in height; it diminishes in size as the climate becomes warmer and dryer further north. It has thin, mottled grey, smooth or grooved bark, and tomentose young stems. The alternate dull green leaves are 15–27 cm (6–11 in) long, and 1–2 cm (⅓–⅔ in) wide, with toothed leaf margins made up of triangular lobes, and often a wavy surface.

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. 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 follicles. Oval or oblong in shape and initially covered in fine hairs, these follicles are from 14 to 20 mm (0.55–0.8 in) long and 6–11 mm (0.25–0.4 in) wide, and protrude 3–6 mm (0.1–0.25 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 mm (0.3–0.4 in) long by 5–6 mm (0.2–0.25 in) wide with a membranous 'wing'.

The root system consists of a main sinker root, and up to ten lateral roots extending from a non-lignotuberous root crown. The main sinker root grows straight down to the water table; it may be up to 15 m (50 ft) long if the water table is that deep. Typically from 3 to 5 cm (1.4–2 in) in diameter immediately below the root crown, roots become gradually finer with depth, and may be less than half a centimetre (0.2 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 cm (2.4–4 in). They may extend over 5 m (15 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 roots, which function throughout the wetter months before dying off with the onset of summer.