The green links below add additional plants to the comparison table. Blue links lead to other Web sites.
enable glossary links

alpine willow-herb, pimpernel willow-herb, épilobe à feuilles de mouron

brook spike-primrose, brook willowherb, narrow boisduvalia, stiff spikeprimrose, Torrey's epilobium, Torrey's willowherb

Habit Herbs with spreading thin, small-leafed epigeous soboles to 5 cm. Herbs with taproot.
Stems

many, ascending, often sigmoidally bent, nodding distally, later erect, clumped or mat-forming, terete, 3–20(–25) cm, simple, subglabrous, sometimes with faint raised strigillose lines decurrent from margins of petioles, rarely mixed strigillose and sparsely glandular puberulent distally.

erect, terete, (1–)4–65 cm, usually with several erect or ascending virgate branches proximally or simple, densely villous, sometimes mixed strigillose, or sometimes subglabrous.

Leaves

opposite and crowded proximal to inflorescence, alternate distally, petioles 1–6 mm, rarely subsessile distally;

blade spatulate to oblong proximally, elliptic to narrowly lanceolate or sublinear distally, (0.5–)0.8–2.5 × 0.3–1 cm, base attenuate to cuneate, margins subentire proximally, sparsely denticulate distally with 2–5 low teeth per side, veins obscure, 2–4 per side, apex obtuse or rounded proximally to subacute distally, surfaces subglabrous;

bracts reduced, usually much narrower.

opposite only in proximal pairs, distally alternate, subsessile, blade linear-lanceolate to very narrowly elliptic, 0.5–4.5 × 0.2–0.3(–0.6) cm, usually longer than internodes, base cuneate, margins subentire to sparsely serrulate, 2–5 low teeth per side, lateral veins obscure, 2–5 per side, apex acute, surfaces subglabrous proximally to densely villous and/or strigillose distally;

bracts slightly reduced.

Inflorescences

nodding in bud, later suberect, few-flowered racemes, subglabrous to sparsely strigillose and/or glandular puberulent.

erect spikes, simple or sparsely branched, ± densely villous and/or strigillose.

Flowers

suberect;

buds 2–5 × 1–2 mm;

pedicel 1–6(–15) mm;

floral tube 0.6–1.2 × 0.8–1.8 mm, slightly raised subglabrous ring at mouth inside;

sepals green to reddish purple, 1.5–5 × 0.6–1.5 mm, abaxial surface subglabrous to sparsely glandular;

petals usually pink to rose-purple, rarely white, narrowly obcordate, (1.7–)2.5–6.5(–8) × 1.6–3.5 mm, apical notch 0.5–1.2 mm;

filaments cream to light pink, those of longer stamens 1.4–3.2 mm, those of shorter ones 0.7–2 mm;

anthers 0.3–0.6 × 0.2–0.4 mm;

ovary often reddish purple, 6–20 mm, subglabrous or sparsely strigillose and glandular puberulent;

style white, 1.2–2.5 mm, glabrous, stigma broadly clavate to subcapitate, entire, 0.9–1.5 × 0.4–0.7 mm, surrounded by longer anthers.

erect, often initiating in most proximal nodes, usually cleistogamous;

buds 0.8–1.5 × 0.5–1 mm;

floral tube 0.4–1 × 0.6–1.2 mm, ring of lax hairs near base inside;

sepals 0.7–2 × 0.4–0.8 mm;

petals pink with darker veins or white, 1.2–3.2 × 0.9–1.8 mm, apical notch 0.4–1 mm;

filaments pale pink, those of longer stamens 0.4–1.8 mm, those of shorter ones 0.3–1 mm;

anthers 0.3–0.6 × 0.3–0.4 mm, apiculate;

ovary 3–6 mm, densely pubescent;

style pale pink, 1.2–2.8 mm, stigma clavate to subcapitate or irregularly 4-lobed, 0.5–1.2 ×0.3–0.6 mm, surrounded by longer anthers.

Capsules

slender, often reddish purple, 17–40(–55) mm, surfaces subglabrous or with scattered hairs;

pedicel 5–35(–68) mm.

cylindrical to subfusiform, terete to slightly 4-angled, (6–)8–14 × 1.1–2 mm, beak 2–3 mm, central column disintegrating, villous;

sessile.

Seeds

narrowly obovoid, 0.7–1.4 × 0.3–0.5 mm, inconspicuous chalazal collar 0.1–0.2 mm wide, light brown, surface reticulate (smooth);

coma persistent, dull white, 2–4 mm.

3–6 per locule, irregularly angular-oblong or fusiform, 0.9–1.6 × 0.4–0.9 mm, chalazal collar absent, brown, surface irregularly reticulate.

2n

= 36.

= 18.

Epilobium anagallidifolium

Epilobium torreyi

Phenology Flowering Jun–Sep. Flowering May–Aug.
Habitat Moist flats, stream banks, subarctic coastal marsh edges, high montane and alpine meadows and seeps. Moist places along stream banks, seasonal streambeds, seeps, and roadside ditches, often in gravelly red or granite soil.
Elevation 0–4500 m. [0–14800 ft.] 0–2600 m. [0–8500 ft.]
Distribution
from FNA
AK; CA; CO; ID; ME; MT; NH; NV; OR; UT; WA; WY; AB; BC; NL; NT; NU; QC; YT; Greenland; Eurasia
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; ID; NV; OR; WA; BC
[WildflowerSearch map]
[BONAP county map]
Discussion

Epilobium anagallidifolium is widely but sparsely distributed in high montane-alpine and subarctic Eurasia, including Europe, Russia, China, and Japan.

Epilobium anagallidifolium usually forms low clumps or mats, with stems nodding in bud and usually subglabrous below the inflorescence. Many collections of E. anagallidifolium from eastern Canada and Greenland tend to be unusually tall (to 25 cm) and robust for the species, with somewhat larger, thicker leaves, and longer pedicels (to 60 mm). Similarly large and robust specimens occur scattered in Yukon and Washington, and may result from occasional hybridization and introgression with sympatric species such as E. hornemannii or E. lactiflorum, which also have the CC chromosomal arrangement. In an analysis of Fennoscandian populations of the Alpinae group, I. Kytövuori (1972) found a similar pattern of mostly smaller, sigmoidal plants of E. anagallidifolium with a small proportion of larger ones, and he also suggested the possibility of hybridization and/or introgression.

Plants of Epilobium anagallidifolium, and indeed of the whole Alpinae group, from Haida Gwaii (the Queen Charlotte Islands) of British Columbia (J. A. Calder and R. L. Taylor 1968), are particularly distinctive compared to those on the mainland, and difficult to interpret. The observed differences may be the result of hybridization with other sympatric species or a response to unique ecological conditions on the islands, reinforced by relative isolation from mainland British Columbia.

The Linnaean name Epilobium alpinum has long been a source of nomenclatural confusion and instability, since it circumscribed at least four distinct species, especially E. anagallidifolium. A proposal by P. C. Hoch et al. (1995) to permanently reject the name E. alpinum Linnaeus was approved.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Epilobium torreyi is an annual species that has a unique gametic chromosome number of n = 9, the lowest found in the genus. Its morphological similarity to Epilobium pallidum (n = 10) suggested to P. H. Raven and D. M. Moore (1965) that E. torreyi may be an aneuploid derivative of E. pallidum or a close relative.

No natural hybrids among species of sect. Pachydium have been reported, but in fact such plants might be difficult to detect. S. R. Seavey (1992) was able to form hybrids, but they were highly sterile. Nevertheless, hybridization between species with n = 9 and n = 10, followed by polyploidization, may well have given rise to the South American species of this section, Epilobium subdentatum (n = 19).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Parent taxa Onagraceae > subfam. Onagroideae > tribe Epilobieae > Epilobium > sect. Epilobium Onagraceae > subfam. Onagroideae > tribe Epilobieae > Epilobium > sect. Pachydium
Sibling taxa
E. arcticum, E. brachycarpum, E. campestre, E. canum, E. ciliatum, E. clavatum, E. cleistogamum, E. coloratum, E. davuricum, E. densiflorum, E. densum, E. foliosum, E. glaberrimum, E. hallianum, E. hirsutum, E. hornemannii, E. howellii, E. lactiflorum, E. leptocarpum, E. leptophyllum, E. luteum, E. minutum, E. mirabile, E. montanum, E. nevadense, E. nivium, E. obcordatum, E. obscurum, E. oreganum, E. oregonense, E. pallidum, E. palustre, E. parviflorum, E. rigidum, E. saximontanum, E. septentrionale, E. siskiyouense, E. smithii, E. suffruticosum, E. torreyi
E. anagallidifolium, E. arcticum, E. brachycarpum, E. campestre, E. canum, E. ciliatum, E. clavatum, E. cleistogamum, E. coloratum, E. davuricum, E. densiflorum, E. densum, E. foliosum, E. glaberrimum, E. hallianum, E. hirsutum, E. hornemannii, E. howellii, E. lactiflorum, E. leptocarpum, E. leptophyllum, E. luteum, E. minutum, E. mirabile, E. montanum, E. nevadense, E. nivium, E. obcordatum, E. obscurum, E. oreganum, E. oregonense, E. pallidum, E. palustre, E. parviflorum, E. rigidum, E. saximontanum, E. septentrionale, E. siskiyouense, E. smithii, E. suffruticosum
Synonyms E. alpinum, E. pseudoscaposum Oenothera torreyi, Boisduvalia parviflora, B. stricta, B. torreyi, Gayophytum strictum, Oenothera densiflora var. tenella
Name authority Lamarck in J. Lamarck et al.: Encycl. 2: 376. (1786) (S. Watson) Hoch & P. H. Raven: Phytologia 73: 458. (1993)
Source FNA vol. 10. Treatment author: Peter C. Hoch. FNA vol. 10. Treatment author: Peter C. Hoch.
Web links