Epilobium obcordatum
heart willowweed, rock fringe, rockfringe willowherb, rose willowherb
many, decumbent to ascending, clumped or cespitose, green to grayish green, terete, 5–15 cm, branched mainly proximally, subglabrous and ± glaucous proximal to inflorescence, ± canescent distally or throughout.
opposite proximal to inflorescence, alternate distally, usually crowded and exceeding internodes, subsessile or petiole 1–2 mm;
blade green or grayish green, usually broadly lanceolate-elliptic to ovate or obovate, rarely suborbiculate, 0.6–2.4 × 0.4–1.3(–1.9) cm, base rounded to subcordate, margins low denticulate, 4–9 teeth per side, veins indistinct, 4–7 per side, apex obtuse proximally to acute distally, surfaces usually subglabrous, rarely canescent, especially on margins and veins;
bracts much reduced.
ascending to erect, sparse racemes or loose panicles, ± densely canescent and glandular puberulent.
erect;
buds 7–13 × 3–5 mm, apex acute, sometimes with stigma exserted;
pedicel 3–10 mm;
floral tube 3.2–5.5 × 2.2–4.2 mm, slightly raised ring of spreading hairs0.4–1 mm from base inside;
sepals (5–)8.5–14 ×1.8–2.9 mm;
petals pink to rose-purple, obcordate, (12–)15–26 × (7–)9–14.6 mm, apical notch 2.5–7.2 mm;
filaments cream to pink, those of longer stamens 8.5–16 mm, those of shorter ones 5.5–11 mm;
anthers cream-yellow, 1.6–2.9 × 0.6–1.3 mm;
ovary 9–22 mm, usually canescent and glandular puberulent, rarely subglabrous;
style cream to light pink, 11–23 mm, glabrous, stigma deeply 4-lobed, 1–1.5 × 2.2–4.5 mm, exserted beyond anthers.
straight, subclavate, 16–40 mm, surfaces canescent and glandular puberulent;
pedicel 5–15 mm.
narrowly obovoid, 1.4–2.1 × 0.6–0.9 mm, with low chalazal collar 0.4–0.5 mm wide, light or grayish brown, surface papillose;
coma easily detached, tawny, 5–9 mm.
= 36.
Epilobium obcordatum
Epilobium obcordatum is an uncommon but relatively widespread and very characteristic species of the high Sierra Nevada, extending to scattered high ranges in northeastern Nevada, Idaho, and southeastern Oregon (Steens Mountains). Its low, clumped habit, dense green and often glaucous foliage, and large flowers make it one of the more attractive species of the genus, with considerable potential as a cultivated plant in rock gardens. Although it bears some general morphological similarities with two species in western North America, E. rigidum and E. siskiyouense, as discussed under those taxa, E. obcordatum also bears close resemblance to E. nankotaizanense Yamamoto, an alpine endemic from Taiwan, China (Chen C. J. et al. 1992). It is uncertain whether they are actually related or have evolved similar morphologies independently in similar high montane habitats on either side of the north Pacific.
Little has been reported on the pollination biology of Epilobium obcordatum, but its large flowers with marked protandry and herkogamy strongly suggest that the plants are outcrossing, probably pollinated by large bees.
Epilobium obcordatum shows considerable morphological variation, especially in leaf shape (ranging from narrowly ovate to orbiculate) and pubescence pattern. In the latter, plants mainly in the Sierra Nevada have stems glabrous and often glaucous below the inflorescence and mixed canescent and glandular puberulent distally. Plants mainly in Idaho and Nevada have stems sparsely to moderately canescent and inflorescences densely mixed canescent and glandular puberulent. But some collections, including the type of E. obcordatum var. puberulum, are mixed, and these pubescence differences do not correlate with other morphological or eco-geographical characters.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
CA
OR
Flora NW
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
