Epilobium anagallidifolium
Epilobium luteum
alpine willow-herb, pimpernel willow-herb, épilobe à feuilles de mouron
yellow willowherb
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.
several, ascending to suberect, loosely clumped, subterete, 15–75 cm, simple or sparsely branched distally, subglabrous proximal to inflorescence with densely strigillose lines decurrent from margins of petioles, mixed strigillose and glandular puberulent distally.
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 proximal to inflorescence, alternate distally, petioles 1–3 mm proximally, subsessile distally;
blade ovate or elliptic, 2.5–7.8 × 1.2–3.5 cm, base attenuate, margins denticulate with 8–20 low, ± pellucid teeth per side, 4–7 prominent veins per side, apex acute to acuminate, surfaces subglabrous with scattered strigillose hairs on margin and abaxial midrib;
bracts much reduced, narrower, more acuminate and denticulate.
nodding in bud, later suberect, few-flowered racemes, subglabrous to sparsely strigillose and/or glandular puberulent.
nodding, later erect, racemes, congested, simple to sparsely branched, densely mixed strigillose and glandular puberulent.
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;
buds 6–10 × 4–5 mm;
pedicel 5–8 mm;
floral tube 1.2–3 × 3–4.6 mm, ring of spreading hairs at mouth inside;
sepals greenish cream, lanceolate, 10–12 × 3–3.5 mm, abaxial surface densely glandular puberulent;
petals cream to pale yellow, 12–22 × 9–13 mm, broad apical notch 1.2–2.4 mm;
filaments cream, those of longer stamens 13–16.5 mm, those of shorter ones 10–15 mm;
anthers yellow, 2.2–3 × 0.7–1.3 mm;
ovary 20–35 mm, densely glandular puberulent;
style cream, 15–22 mm, stigma 4-lobed, 1–2 × 2.8–4.5 mm, lobes spreading to recurved, strongly exserted beyond anthers.
slender, often reddish purple, 17–40(–55) mm, surfaces subglabrous or with scattered hairs;
pedicel 5–35(–68) mm.
erect, 35–75 mm, surfaces sparsely glandular puberulent;
pedicel 10–22 mm.
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.
narrowly fusiform or oblanceoloid, 1–1.2 × 0.4–0.5 mm, chalazal collar 0.06–0.1 mm, surface reticulate;
coma persistent, tawny, 6.5–8 mm.
= 36.
= 36.
Epilobium anagallidifolium
Epilobium luteum
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 luteum is one of the most distinctive species in the genus due to its large creamy flowers, a color otherwise known only in the distantly related E. suffruticosum. It appears that E. luteum is most closely related to species of the Alpinae group, sharing not only similarities in perennating habit and structures, but also the derived CC chromosome arrangement (S. R. Seavey and P. H. Raven 1977, 1978).
Because Epilobium luteum is modally outcrossing and commonly pollinated by bees, it sometimes hybridizes with several other species of Epilobium when they grow sympatrically. One recurrent hybrid combination is E. luteum × E. ciliatum subsp. glandulosum, first described and named E. ×treleasianum H. Léveillé, and later E. luteum var. lilacinum L. F. Henderson. Following a suggestion by P. A. Munz (1965) that E. ×treleasianum was a hybrid of that particular parentage, S. R. Seavey (1993) verified the relationship in a series of crossing experiments. Epilobium ×treleasianum occurs over a wide geographical range in Alaska, British Columbia, and Washington, forming repeatedly when the parental species co-occur, and often backcrossing with one or both parents, forming hybrid swarms with varying morphological combinations. It also grows vigorously vegetatively.
Another less common hybrid of Epilobium luteum was described as E. ×pulchrum Suksdorf, and a minor variant as E. ×pulchrum var. albiflorum Suksdorf (S. R. Seavey 1993). The second parent of these hybrids is less obvious, but based on morphological features, it is most likely E. hornemannii, which also grows frequently in sympatry with E. luteum.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
- Local floras:
BC, 
CA, 
OR, 
WA - Local Web sites: CalFlora, CalPhotos,
Flora NW, 
Go Botany, 
PNW Herbaria, 
SW CO Wildflowers, Turner Photog. 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
- Local floras: BC, CA, OR, WA
- Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria, Turner Photog.
- WildflowerSearch
- iNaturalist (observations)
- USDA Plants Database
- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
