Pterostylis aspera, commonly known as the rough shell orchid, is a species of orchid endemic to the south-west of Western Australia. As with similar greenhoods, the flowering plants differ from those which are not flowering. The non-flowering plants have a rosette of leaves flat on the ground but the flowering plants have a single flower with leaves on the flowering spike. In this common species, the flower is white with green and reddish-brown stripes and a short, straight labellum.
Pterostylis aspera is a terrestrial, perennial, deciduous, herb with an underground tuber and when not flowering, a rosette of bluish-green leaves lying flat on the ground. Each leaf is NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide. Flowering plants usually only have a single flower NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide which leans forwards on a flowering stem NaNsigfig=1NaNsigfig=1 high. There are between three and five stem leaves NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide . The flowers are white with green and reddish-brown stripes. The dorsal sepal and petals are fused, forming a hood or "galea" over the column and the dorsal sepal has a sharp point. The lateral sepals are held closely against the galea and have narrow tips NaNsigfig=2NaNsigfig=2 long and a broad sinus with a small notch between their bases. The labellum is NaNsigfig=1NaNsigfig=1 long, about 4sigfig=1NaNsigfig=1 wide, relatively straight, and only just visible above the sinus. Flowering occurs from May to July.[1] [2] [3]
Pterostylis aspera was first formally described in 1989 by David Jones and Mark Clements from a specimen collected near Eaton and the description was published in Australian Orchid Research.[4] The specific epithet (aspera) is a Latin word meaning "rough", "harsh" or "uneven",[5] referring to hairs on the labellum.
The rough shell orchid grows in shrubland and woodland between Dongara and Jerramungup in the Avon Wheatbelt, Esperance Plains, Jarrah Forest, Mallee and Swan Coastal Plain biogeographic regions.
Pterostylis aspera is listed as "not threatened" by the Government of Western Australia Department of Parks and Wildlife.