(pimpernel willowherb)
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Photo of Epilobium anagallidifolium by Mary Beth Cook
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Epilobium anagallidifolium is a delicate perennial herb in the evening primrose family (Onagraceae) found in moist, lush meadows and tundra. It grows up to 20 cm tall from fibrous roots, is often matted with basal offshoots, and stems that are curvy, weak, and usually reddish-tinged. The leaves are opposite,
elliptic to
oblong, up to 2.5 cm long and 9 mm wide,
simple,
glabrous, and with
entire margins. The
inflorescence is a few-flowered (1-3) nodding
raceme (in bud and flower), the flower is
radially symmetric, pink to rose-purple petals up to 9 mm long and eight
stamens. The fruit is an upright
dehiscent capsule, 2-3 cm long. Seeds have a tuft of long silky hairs to aid in dissemination by wind. It is distinguished from the other small-flowered, short-statured species in the genus by having sessile, unwinged lower leaves (or with
petioles up 3 mm long), nodding buds and
glabrous inflorescences. It is most similar to
E. hornemannii but that species is generally larger and stouter, has serrated leaves and
glandular inflorescences. The species name likely refers to the resemblance of its leaves to those of
Anagallis, or 'pimpernel', a common genus in the Pink family in Europe.
This species flowers in mid-summer.
Plants are
monoecious, with bisexual flowers. The closed morphology of the flowers indicates flowers may be self-compatible. This was substantiated by a genetic study which found populations were very homogenous, indicating high rates of self-fertilization (
Kelley and Latta 1998). Seeds have a long tuft of white hairs, to aid wind dispersal.
Two rust fungi are known to occur on the leaves or stems of
Epilobium anagallidifolium :
Puccinia epilobii and
Pucciniastrum epilobii;
Abies grandis is an alternate host of the later (
Peat et al. 2015).
Epilobium anagallidifolium is a circumpolar species. In North America this species occurs in the Alaska and the Yukon mostly south of the 66th parallel, to Newfoundland, south into Maine in the east, and Colorado and California in the west. It occurs occasionally in suitable habitat on both sides of the Alaska Range in Denali, where it is more common on the southern slopes in the Cook Inlet basin than to the north.
Details are shown in the Plots & Charts found at right, depicting recent Denali data.
Throughout its global range Epilobium anagallidifolium occurs in all vegetation zones from seashores to the alpine. From Alaska on south to California it is mostly found in the mountains. In Denali it is found from 158-1470 m, but most occurrences are between 900-1100 m with an average of 1043 m. Compared to other species in the genus in Denali, it is most similar to E. hornemannii in altitudinal distribution. There is no preference for aspect in the occurrences in Denali, it occurs almost equally on north and south-facing slopes. It occurs on flat terrain up to 40 degree slopes with most occurrences between 10-28 degrees and slightly greater amplitude on south-facing slopes.
Details are shown in the Plots & Charts found at right. For more on how to interpret these figures, visit Understanding Data Presented.
Epilobium anagallidifolium is a plant of moist alpine slopes, meadows, seepage areas, margins of ponds, marshes and streambanks.
Moist to wet sites in the mountains.
