Banksia (Banksia petiolaris)

Description

Banksia petiolaris is a prostrate shrub that can spread to a diameter of 2 metres (6 1⁄2 feet). Its thick stems grow horizontally on the ground and are covered in fine hair. The new growth is more densely covered with velvety orange brown hair. The large, leathery, upright leaves arise vertically on petioles up to 15 cm (6 in) high. The upper surface faces north and is inclined at around 15 degrees off vertical. The leaf blades can reach 60 cm (24 in) in length and 4 cm (1 1⁄2 in) wide. They are dull green with serrated margins and a white undersurface. Dead leaves remain on the plant. Flowering occurs in late spring. The cylindrical inflorescences are yellow in overall colour and range from 9 to 16 cm (3 1⁄2 to 6 1⁄4 in) high. As the flower spikes age, they fade to a greyish colour, the old flowers persisting. Up to 20 woody seed pods, known as follicles, may appear on each spike. Covered with a fine grey fur, they are elliptical in shape and measure 2.8–3.8 cm (1 1⁄8–1 1⁄2 in) in length, and 1.5–2 cm (5⁄8–3⁄4 in) in width.The obovate (egg-shaped) seed is 2.5–2.8 cm (1–1 1⁄8 in) long and fairly flattened. It is composed of the triangular seed body (containing the embryonic plant), measuring 1.0–1.5 cm (3⁄8–5⁄8 in) long by 1.4–2.0 cm (1⁄2–3⁄4 in) wide, and a papery wing. One side, designated the outer surface, is deeply pitted and the other is brown and smooth. The seeds are separated by a sturdy dark brown seed separator that is roughly the same shape as the seeds with a depression where the seed body sits adjacent to it in the follicle. The first pair of leaves produced by seedlings, known as cotyledons, are cuneate (wedge-shaped) and measure 1.2–1.4 cm (1⁄2–9⁄16 in) long by 1.8–2.0 cm (11⁄16–13⁄16 in) wide. They are dull-green with a faint net-like pattern. The auricle at the base of the cotyledon leaf is pointed and measures 0.2 cm (1⁄16 in) long. The first pair of leaves to appear after the cotyledons are 3.5 cm (1 3⁄8 in) long and oval in shape, with 2–3 lobes or teeth on each side. The next set are 5 cm (2 in) long with 7–10 teeth.B. petiolaris is fairly uniform across its range, though plants may vary in leaf size. Its yellow flower spikes and white leaf undersurface distinguish it from other prostrate banksias.