Pterostylis pusilla, commonly known as the tiny rustyhood is a plant in the orchid family Orchidaceae and is endemic to southern Australia. It has a rosette of leaves and up to nine relatively small green and reddish-brown flowers with translucent white "windows" and a dark brown, insect-like labellum.
Pterostylis pusilla is a terrestrial, perennial, deciduous, herb with an underground tuber. It has a rosette of between three and eight leaves, each leaf NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide. Flowering plants have a rosette at the base of the flowering stem and up to nine green and reddish-brown flowers with translucent white panels and which are NaNsigfig=1NaNsigfig=1 long and about 5sigfig=2NaNsigfig=2 wide on a flowering stem NaNsigfig=1NaNsigfig=1 tall. There are between two and four stem leaves with their bases wrapped around the flowering stem. The dorsal sepal and petals are fused to form a hood called the "galea" over the column, with the dorsal sepal having a narrow, upturned point NaNsigfig=1NaNsigfig=1 long. The lateral sepals turn downwards, much narrower than the galea and have thread-like tips NaNsigfig=1NaNsigfig=1 long. The labellum is relatively thick, reddish-brown and insect-like, about 4sigfig=1NaNsigfig=1 long and 2sigfig=1NaNsigfig=1 wide. The "head" end has many short hairs and there are between two and four longer hairs on each side of the body. Flowering occurs from September to October.[1] [2] [3]
Pterostylis pusilla was first formally described in 1918 by Richard Rogers from specimens sent to him from South Australia and Victoria. The description was published in Transactions and Proceedings of the Royal Society of South Australia.[4] [5] The specific epithet (pusilla) is a Latin word meaning "very little", "small", "petty", "puny" or "insignificant".[6]
The tiny rustyhood usually grows in leaf litter in open forest or mallee scrub in stony soil. It is found in New South Wales south from Temora, across Victoria and in the south of South Australia in areas with an average annual rainfall of NaNsigfig=1NaNsigfig=1.[7]