Banksia petiolaris is a rare species of flowering plant in the family Proteaceae native to Western Australia, where it is found in sandy soils in the south coastal regions from Munglinup east to Israelite Bay. It was first described by Victorian state botanist Ferdinand von Mueller in 1864, and no subspecies are recognised. B. petiolaris is one of several closely related species that will all grow as prostrate shrubs, with horizontal stems and thick, leathery upright leaves. Those of this species can be viable for up to 13 years—the longest-lived of any flowering plant recorded. It bears yellow cylindrical flower spikes, known as inflorescences, up to high in spring. As the spikes age, they turn grey and develop up to 20 woody seed pods, known as follicles, each. Insects such as bees, wasps and even ants can pollinate the flowers. B. petiolaris is nonlignotuberous, meaning it regenerates by seed after bushfire. B. petiolaris adapts readily to cultivation, growing in well-drained sandy soils in sunny locations. It is suitable for rockeries and as a groundcover. Description Banksia petiolaris is a prostrate shrub that can spread to a diameter of . 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 high. The upper surface faces north and is inclined at around 15 degrees off vertical. The leaf blades can reach in length and 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 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 in length, and in width. The obovate (egg-shaped) seed is long and fairly flattened. It is composed of the triangular seed body (containing the embryonic plant), measuring long by 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