About Pterostylis irsoniana Hatch
Pterostylis irsoniana is a terrestrial, perennial, deciduous herb that grows from an underground tuber. It produces three to five stem leaves, which increase in size moving up the stem; the largest leaf reaches up to 180 mm (7 in) long and 12 mm (0.5 in) wide. The leaves are linear to lance-shaped, green with a reddish tinge, and the topmost leaf grows taller than the plant's flower. A single dark green flower, which has a reddish tinge near its tips, is borne on a flowering stem that grows up to 350 mm (14 in) tall. The dorsal sepal and petals are fused together to form a hood, called a "galea", that covers the column. The dorsal sepal is 15–30 mm (0.6–1 in) long, curves forward, and ends in a short pointed tip. The lateral sepals are erect, held in close contact with the galea, and their tips spread slightly apart from one another. The labellum curves gently along most of its length, then suddenly curls downward at its tip, and bears a dark red or blackish callus. Flowering takes place between October and January. This greenhood orchid grows in grass, montane Nothofagus forests, and subalpine Podocarpus scrub, most often in deep leaf litter or on the edges of bogs. In New Zealand's North Island, it is found from East Cape to Wellington, and in the South Island it occurs on the western side as far south as Haast.
