Pterostylis arbuscula is a terrestrial,
perennial,
herb that typically grows to a height of tall and has a
rosette of egg-shaped leaves long and wide on a
petiole up to long, and borne above ground level. There are 5 to 8 dark green leaves on the stem that are elliptic to egg-shaped, long wide. Up to 3 more or less "nodding", dark reddish-brown to green, white banded flowers long and wide are borne on a
pedicel and long. The
dorsal sepal is long, the
lateral sepals are long and wide. The petals are long and about wide and translucent with reddish-brown lines. The labellum is egg-shaped with the narrower end towards the base, long and wide. Flowering occurs from June to late August. ==Taxonomy and naming==