Perennial herbs, often flowering the first year, or sometimes annual (not in Taiwan) or woody, perennating by leafy rosettes, stolons, soboles, turions, axillary buds, or spreading lateral roots (the latter two modes not in Taiwan). Stems erect, ascending, or decumbent, glabrous to densely pubescent and/or glandular, often with raised lines of hairs decurrent from the margins of the petioles. Leaves sessile to petiolate, generally opposite below (rarely whorled) to alternate on inflorescence, subentire to denticulate; stipules absent. Flowers in loose bracted racemes (or panicles), 4-merous, generally actinomorphic, rose-purple or white (elsewhere rarely red-orange or cream); floral tube present; sepals 4, erect; petals 4, generally apically notched; stamens 8; pollen shed in tetrads (or monads, not in Taiwan); stigma entire (clavate to capitate) to 4-lobed. Fruit an elongate, slender, 4-loculate, subterete capsule, readily dehiscent. Seeds generally in 1 row per chamber, mostly narrowly obovoid, each with a coma (absent in a few non-Taiwanese taxa). 2n=24, 26, 30, 32, 36, 60, 72, 108; all species counted in Taiwan have 2n=36.
A genus of some 170 species widely distributed in cool temperate and montane regions worldwide, with most smaller sections restricted to the New World. Most species (ca. 150), including all seven Taiwanese species, are placed in sect. Epilobium. Four of the seven Taiwanese taxa are endemic to the island while the other three have much broader ranges in Asia. Hybridization between species of Epilobium has been documented in other parts of the world. When present, the perennating features at the base of a plant may provide useful information in the identification of that plant to species.
Chen, C. J., Hoch, P. C. & Raven, P. H. 1992. Systematics of Epilobium (Onagraceae) in China. Syst. Bot. Monogr. 34: 1-209.
