Pterostylis aciculiformis, is a terrestrial,
perennial,
deciduous,
herb with an underground tuber. It has a
rosette of between five and twelve leaves at the base of the flowering spike, each leaf long and wide. Up to twelve green and brown flowers long and wide are borne on a flowering spike tall. Three to six stem leaves are wrapped around the flowering spike. The
dorsal sepal and
petals form a hood over the column with the dorsal sepal having an upturned point about long. The
lateral sepals turn downwards, curve forwards and are narrower than the hood. They have thread-like tips long and are more or less parallel to each other. The
labellum is brown, fleshy and insect-like, about long and wide. The "head" end is swollen, there are 6 to 12 white bristles on each side and many short bristles on the "tail" end. Flowering occurs from September to December. ==Taxonomy and naming==