Family: Onagraceae
Fireweed, Willow-Herb
Epilobium image
Emmet J. Judziewicz  

Key to Wisconsin Eqilobium

    • 1a.Taprooted annuals; lower part of stem with an exfoliating outer layer; leaves narrow, linear, less than 3 mm wide, glabrous; opposite only on the lowermost part of the stem, alternate in the extensive dichotomously-branching inflorescence E. bracgycarpum

    • 1b.Fibrous-rooted, often rhizomatous perennials; cortex of stem not cracking and exfoliating; most leaves (except on E. leptophyllum) more than 3 mm wide, at least sparsely or minutely pubescent; leaves opposite up to about midstem; inflorescence not extensive and not dichotomously branching 2

    • 2a.Stems pubescent with horizontally spreading (not incurved) hairs 3

    • 2b.Stems and leaves pubescent with mostly incurved hairs, or nearly glabrous 5

    • 3a.Stigmas entire; plants pubescent with dense short, straight, spreading and glistening hairs; leaves narrowly lanceolate, less than 8 mm wide, margins entire and revolute; petals pinkish, entire E. strictum

    • 3b.Stigmas deeply 4-cleft; plants pubescent with mixed short and longer hairs; larger leaves more than 1 cm wide, toothed or denticulate; petals pink or purple, notched 4

    • 4a.Leaves sessile, most clasping the stem or slightly decurrent; petals 10--20 mm long, purple, shallowly notched E. hirsutum

    • 4b.Leaves subsessile, not clasping or decurrent; petals 4--9 mm long, pale pink or purple, deeply notched E. parviflorum

    • 5a.Leaves entire or subentire, the margins often revolute; stem terete, without decurrent lines from the base of each leaf, minutely pubescent or canescent 6

    • 5b.Leaves flat, not revolute, conspicuously toothed or with gland-like denticulations;stem more-or-less 4-angled, with decurrent lines, angles, or strips of pubescence running down from the leaf bases 7

    • 6a.Most leaves linear to oblong-lanceolate, 3--12 mm wide; upper leaf surface glabrous except scaberulous along the margin or with scattered hairs along the midrib; tip of stem nodding before flower buds open E. palustre

    • 6b.Most leaves linear, 1--3 mm wide; upper leaf surface densely pubescent with minute, incurved hairs; tip of stem erect E. leptophyllum

    • 7a.Leaves lanceolate to narrowly ovate, acute, nearly sessile; teeth on leaf margins 15--40, little more than gland-like denticulations; stem internodes with scattered pubescence; mature seeds striate, with a short beak and a whitish coma E. ciliatum

    • 7b.Leaves long lanceolate, acuminate, with petioles 2--6 mm long; teeth on leaf margins 30--75, distinct between irregular rounded sinuses; stem internodes pubescent in decurrent lines; mature seeds papillose, beakless, with a coppery or cinnamon brown coma E. coloratum

About 170 species worldwide in cool temperate climates, mostly perennial polyploid herbs, often self-pollinating, but taxonomically difficult due in part to frequent hybridization.