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FNA | Family List | FNA Vol. 10 | Onagraceae | Epilobium

15. Epilobium obcordatum A. Gray, Proc. Amer. Acad. Arts. 6: 532. 1865.


Epilobium obcordatum var. puberulum Jepson

Herbs ± suffruticose, wiry shoots from woody caudex with barklike periderm extending to 25 cm below ground, shoots with scaly bases. Stems 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. Leaves 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. Inflorescences ascending to erect, sparse racemes or loose panicles, ± densely canescent and glandular puberulent. Flowers 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. Capsules straight, subclavate, 16–40 mm, surfaces canescent and glandular puber­ulent; pedicel 5–15 mm. Seeds 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. 2n = 36.

Flowering Jul–Sep. Dry, rocky montane or alpine ridges, basaltic cliffs, along edges of talus or gravel slopes; 1900–4000 m; Calif., Idaho, Nev., Oreg.

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.


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