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

14. Epilobium septentrionale (D. D. Keck) R. N. Bowman & Hoch, Ann. Missouri Bot. Gard. 66: 897. 1980.

Northern willowherb

Zauschneria septentrionalis D. D. Keck, Publ. Carnegie Inst. Wash. 520: 219, figs. 84 [top center], 85 [upper right]. 1940; Epilobium canum (Greene) P. H. Raven subsp. septentrionale (D. D. Keck) P. H. Raven

Herbs usually not suffruticose, with basal shoots from thick­ened caudex, often decussate scales at base. Stems decumbent, often matted, grayish green, terete, 5–25 cm, well-branched throughout, densely white-canescent proximally, mixed strigillose, villous, and glandular puberulent distally. Leaves densely spaced, opposite proximal to inflorescence, alternate or fasciculate distally, petiole 0–2 mm, blade grayish green to green, lanceolate or elliptic to narrowly ovate, 1–3.5(–4) × 0.4–1.1 cm, base cuneate or attenuate, margins sub­entire to low-denticulate, 5–8 teeth per side, veins inconspicuous, 3–5 per side, apex acute, sometimes with caducous dark mucro, surfaces densely white-canescent and eglandular proximally, changing abruptly on inflorescence to glandular puberulent mixed with scattered villous; bracts somewhat reduced. Inflorescences ascending spikes or racemes, densely glandular puberulent. Flowers: buds 12–15 × 4–5.5 mm, subsessile or pedicels 1–2 mm; floral tube same color as petals, 17–23 × 3.5–5 mm, with ring of scales 4–5 mm from base inside; sepals same color as petals, 7–12 × 2.5–3.5 mm; petals red-orange, 8–14 × 5–6.5 mm, apical notch 1.8–2.4 mm; filaments orange or red, those of longer stamens 15–17 mm, those of shorter ones 13–15 mm; anthers 2.8–3.2 × 0.7–1 mm; ovary 5–11 mm, glandular puberulent; style light orange, 40–45 mm, stigma 4-lobed, 0.9–1.1 × 2.2–2.6 mm, exserted 8–10 mm beyond anthers. Capsules ± straight, 20–26 mm, ± beaked, surfaces glandular puberulent; sessile or pedicel 1–3 mm. Seeds broadly to narrowly obovoid, with constriction 0.7–0.8 mm from micropylar end, 1.8–2.4 × 1.1–1.3 mm, chalazal collar inconspicuous, light brown, surface low-papillose; coma easily detached, dingy white, 6–7 mm. 2n = 30.

Flowering Aug–Sep. Rocky ledges and serpentine slopes along rivers; 10–1900 m; Calif.

Epilobium septentrionale is endemic to northern California, found only in the drainages of the Eel, Mattole, and Trinity rivers in Humboldt, Mendocino, and Trinity counties. The dimorphic pattern of vestiture on this species (eglandular, white-canescent lower leaves versus glandular puberulent upper leaves and bracts) is highly distinctive and not found in any specimens of E. canum. Most collections are relatively uniform in aspect, leaves, flowers, fruits, and seeds, despite the relative isolation from one another in the different river drainages where they occur.

S. R. Seavey and P. H. Raven (1977c) reported an experimental hybrid between Epilobium septentrionale and diploid E. canum subsp. canum; although it had normal chromosome pairing, pollen fertility was reduced (51%).


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