Small-flowered leafy greenhood

Description

Pterostylis diminuta, commonly known as the small-flowered leafy greenhood, is a plant in the orchid family Orchidaceae and is endemic to Victoria. As with similar greenhoods, the flowering plants differ from those that are not flowering. The non-flowering plants have a rosette of leaves flat on the ground but the flowering plants have up to twelve small, partly green, partly translucent flowers and lack a rosette. Pterostylis diminuta, is a terrestrial, perennial, deciduous, herb with an underground tuber. Non-flowering plants have a rosette of between three and six, egg-shaped leaves, each leaf 15–25 mm (0.6–1 in) long and 3–5 mm (0.1–0.2 in) wide. Flowering plants lack a rosette but have up to twelve flowers on a flowering spike 80–400 mm (3–20 in) high with four to seven linear to lance-shaped stem leaves that are 15–80 mm (0.6–3 in) long and 2–4 mm (0.08–0.2 in) wide. The flowers are 10–15 mm (0.4–0.6 in) long, 4–6 mm (0.16–0.24 in) wide. The dorsal sepal and petals are joined to form a hood called the "galea" over the column. The galea is dark green with translucent "windows" and a brownish, tapered tip. The lateral sepals turn downwards and are 8–11 mm (0.3–0.4 in) long, 4–6 mm (0.16–0.24 in) wide and joined for about half their length. The labellum is 4–5 mm (0.16–0.20 in) long, about 2 mm (0.08 in) wide and brownish with a dark stripe along its mid-line. Flowering occurs from September to November. Pterostylis is a genus of about 300 species of plants in the orchid family, Orchidaceae. Commonly called greenhood orchids, they are terrestrial, deciduous, perennial, tuberous, herbs found in Australia, New Zealand, New Guinea, New Caledonia and one Indonesian island. The flowers are mostly green, sometimes with brown, reddish or white stripes, and are distinguished from other orchids by their unusual flower structures and pollination mechanism. Greenhood orchids are all terrestrial herbs with an underground tuber like many other genera of orchids but are distinguished by a hood-like "galea" formed by the fusing of the dorsal sepal and two lateral petals. The galea curves forward, covers the sexual parts of the flower, is important in the pollination process and is about as long as the two petals. The dorsal sepal is translucent white with green, reddish or brown stripes. The two lateral sepals are joined at their base, form the front of the flower and usually protrude to form "points" or "ears" which extend above or to the side of the galea.