Pterostylis patens

Detailed description

Terrestrial, tuberous, glabrous, spring to summer-green perennial herb, forming dense colonies of numerous plants through vegetative extension. Plant at flowering 100–480 mm tall. Stem stiffly erect, smooth, green, dark green to reddish green, internodes very short near base, otherwise shorter than leaves throughout. Leaves 4–6, sessile, stiffly erect, dark green to reddish green with entire margins; in sterile plants lamina of similar size, oblong-elliptic to broadly lanceolate; in flowering plants lamina scarcely changing from base to top of stem; lamina of largest leaves 50–180 × 10–20 mm, broadly lanceolate, lanceolate to linear-lanceolate, prominently and deeply keeled, often with 2–3 laterals on either side of midrib, apex acute, acuminate, base wider than rest of lamina broadening into a long sheathing base; more or less even within base of flower, rarely slightly overtopping flower. Flower solitary, erect, front mostly green finely striped with white, stripes of white widening toward back of galea with green narrowing, with the back often completely. Ovary erect. Dorsal sepal distinctly globose, 40–50 mm tall, erect, distal portion initially horizontal, soon steeply inclined, apex steeply keeled, tapering to a strongly deflexed caudate tip up to 30 mm long. Lateral sepals diverging at a narrow angle, caudae of lobes up to 40 mm long, tapered, strongly deflexed down and sometimes meeting behind ovary. Petals much shorter than dorsal sepal with acuminate apices. Labellum elliptic-oblong, scarcely arched, flat in cross-section, narrowing slightly towards tip, bending forwarding smoothly and symmetrical, protruding from lateral sepals sinus, midrib initially prominent soon evanescent toward the obtuse, emarginate, often cucullate apex. Column as tall as or slightly taller than labellum; stigma ellipsoid, scarcely distinguished from column and rather flat.