"Banksia brownii" usually grows as an upright bush between one and three metres (3–10 ft) high, but it can also grow as an openly branched small tree to six metres (20 ft) in sheltered gullies, or as a low, spreading shrub in exposed locations such as the peaks of the Stirling Range. The bark is a grey-brown colour, smooth and thin, with lenticels. The leaves are long and thin, from three to ten centimetres (1–5 in) long, and five to ten millimetres (– in) wide. Dark green and hairless above but with a hairy white underside, they are easily recognised by their feather-like appearance, caused by the fact that they are finely divided almost back to the midrib, into as many as 70 thin tapered lobes.