1. Triphora trianthophora (Sw.) Rydb. (three‑bird orchid, nodding pogonia)

Pl. 118 a, b; Map 489

Plants with tuberlike root bases and stolons. Flowering stems 8–30 cm long, nodding at the tip, with 2–6 flowers in racemes. Leaves 3–8, alternate on the flowering stems, 6–18 mm long, sessile, narrowly ovate, herbaceous, green, sometimes purple tinged, glabrous. Sepals and lateral petals similar, 10–15 mm long, narrowly oblanceolate, white to light pinkish purple. Lip 10–15 mm long, 3‑lobed, obovate, the margins near the tip usually somewhat irregular and crinkled, white, the middle with 3 low, longitudinal, green ridges. Column 8–10 mm long, white. Stamen 1, staminodes lacking. Capsules erect at maturity, sometimes nodding during development, 10–15 mm long, elliptic in outline, strongly ribbed. July–October.

Scattered in the state, mostly south of the Missouri River (eastern U.S. west to Kansas and Oklahoma; Central America). Mesic forests in ravines and valleys of streams, in bottoms and lower slopes, also in bottomland forests, terrestrial or rarely on rotting logs.

This species often occurs in small colonies of plants that are frequently connected by stolons running between the thickened, tuberlike root bases. Luer (1975) described an interesting phenomenon in which plants in an area are cued by temperature or other climatic conditions to open all mature buds on a single day. The flowers, which last only one day, apparently are pollinated by halictid bees.