General – a low perennial from slender, creeping rhizomes, stems simple, erect, hairless or with tiny glands; growing up to 20 cm tall.
Leaves – simple, in whorls of 5 to 9 at stem tip, with a few small, scale-like leaves below, lance-shaped, 3 – 10 cm long, stalkless or short-stalked, thin, toothless or finely toothed.
Flowers – single, or sometimes 2 or 3, on slender stalks from centre of leaf cluster, white, 8 – 14 mm across; 5 – 9 petals, lance-shaped to egg-shaped, long-pointed; appearing early-summer.
Fruit – a spherical, 5-chambered, few-seeded capsule, dispersed by wind; ripening mid-summer.
Circumboreal; prefers open shade and moist woods; tolerant of all but the poorest soil/site conditions.
In Latin, triens means “the third part.” One explanation for the derivation of the genus name is that the plant is about 4 in. (10 cm high), or 1/3 of a foot.