Nevada willowherb

Herbs with many shoots from thick, woody caudex. Stems erect or ascending, terete, 10–50 cm, branched at base and apically, densely strigillose throughout, sometimes mixed villous distally. Leaves: proximal pairs often early-deciduous, petiole 1–4 mm, blade lanceolate-elliptic to narrowly so, ± folded along midrib, 0.9–1.7 × 0.2–0.6 cm, shorter than internodes, base attenuate or narrowly cuneate, margins denticulate, 6–10 low teeth per side, lateral veins inconspicuous or absent, apex acute with deciduous, rigid mucronate gland, surfaces usually glabrescent with scattered hairs on abaxial midrib, rarely strigillose-villous throughout; bracts much reduced, sublinear, often attached to pedicel. Inflorescences erect, open racemes or panicles, strigillose, often mixed glandular puberulent. Flowers erect to ± nodding; buds rounded-obovoid, 5–6 × 3–4 mm; floral tube with slight constriction 2–3 mm distal to base, 2.7–3.2(–5) × 1.8–2.5(–3.1) mm, without ring or scales inside, glabrous; sepals erect or sometimes deflexed in late anthesis, green or reddish green, lanceolate, 2.6–4.2 × 0.9–1.3 mm, apex acute; petals deep rose-purple, obcordate, 5–7.2 × 3.2–4.1 mm, apical notch 2–3 mm; filaments cream or white, those of longer stamens 5–7.5 mm, those of shorter ones 3.5–5.5 mm; anthers cream, 1–1.8 × 0.5–0.8 mm, scarcely apiculate; ovary 2.5–3.8 mm, densely strigillose and/or glandular puberulent; style cream, 6–9.5 mm, glabrous, stigma 4-lobed, 0.8–1.2 × 1–1.5 mm, lobes reflexed or sometimes incompletely spread, then forming cup-like structure, exserted beyond longer anthers. Capsules erect, subfusiform, 8–12 mm, surfaces strigillose and/or glandular puberulent; pedicel 1–1.8 mm. Seeds obovoid, with constriction 0.6–1 mm from micropylar end, 2.1–2.9 × 1.2–1.5 mm, very inconspicuous chalazal collar 0.05–0.06 mm wide, dark brown, surface low papillose, papillae often with central pit; coma easily detached, white, 6–7.5 mm. 2n = 30.

Flowering Jul–Sep. Loose scree slopes, limestone talus, sandy soils at base of steep rock faces in pinyon pine-juniper-mountain brush communities; 1800–2800 m; Ariz., Nev., Utah.

In his description of Epilobium nevadense, Munz clearly recognized its affinity to E. nivium and suggested a close relationship between these two species and E. brachycarpum, based on similarities in seed and floral morphology. S. R. Seavey and P. H. Raven (1977c) demonstrated the close affinity between E. nivium and E. nevadense by forming fully fertile (99%) hybrids. However, compared to E. nivium, E. nevadense has denticulate, subglabrous leaves (versus subentire, densely pubescent leaves) and shorter floral tube [2.7–3.2(–5) mm] versus longer (5.2–9.5 mm) in E. nivium; furthermore, the two have com­pletely non-overlapping geographical ranges. In overall morphology and cytology, these two species (and the somewhat more distantly related E. suffruticosum) are quite distinct from the rest of the genus.

Originally known only from the Charleston Mountains in southern Nevada, Epilobium nevadense has since been collected in northern Arizona, Eureka and Lincoln counties in Nevada, and in three counties of southwestern Utah. It may be more widespread in this region, much of which (especially in southern Nevada) consists of military reserves that are inaccessible to collectors. Although it was at one time considered endangered (S. D. Ripley 1975) due to the relatively low number of collections and threats from increased recreational use in its area of occurrence, it is no longer considered a candidate for listing (http://endangered.fws.gov). Several collections of this species show evidence of seed predation, apparently by moth larvae (H. N. Mozingo and Margaret Williams 1980), and S. R. Seavey and P. H. Raven (1977c) reported that larvae found in capsules from the locality in the Charleston Mountains were identified as Mompha (Momphidae, Gelechioidea).