Fireweed

Chamerion angustifolium, commonly known as fireweed (mainly in North America), great willow-herb (some parts of Canada), androsebay willow-herb or rosebay willowherb (mainly in Britain),is a perennial herbaceous plant in the willowherb family Onagraceae.

It is native throughout the temperate Northern Hemisphere, including large parts of the boreal forests.

This species has been placed in the genus Chamerion (sometimes, incorrectly, given as Chamaenerion) rather than Epilobium based on several morphological distinctions: spiral (rather than opposite or whorled) leaf arrangement; absence (rather than presence) of ahypanthium; subequal stamens (rather than stamens in two unequal whorls); zygomorphic (rather than actinomorphic) stamens andstigma. Under this taxonomic arrangement, Chamerion and Epilobium are monophyletic sister genera.

Two subspecies are recognized as valid:

•          Chamerion angustifolium subsp. angustifolium
•          Chamerion angustifolium subsp. circumvagum (Mosquin) Hoch

Descroption

The reddish stems of this herbaceous perennial are usually simple, erect, smooth, 0.5–2.5 m (1½–8 feet) high with scattered alternate leaves. The leaves are entire, lanceolate, and pinnately veined. A related species, dwarf fireweed (Chamerion latifolium), grows to 0.3–0.6 m tall.

The flowers have four magenta to pink petals, 2 to 3 cm in diameter. The styles have four stigmas, which occur in symmetrical terminal racemes. The floral formula is ✶/↓ K4 C4 A4+4 or 4+0 Ğ(4).

The reddish-brown linear seed capsule splits from the apex. It bears many minute brown seeds, about 300 to 400 per capsule and 80,000 per plant. The seeds have silky hairs to aid wind dispersal and are very easily spread by the wind, often becoming a weed and a dominant species on disturbed ground. Once established, the plants also spread extensively by underground roots, an individual plant eventually forming a large patch.

The leaves of fireweed are unique in that the leaf veins are circular and do not terminate on the edges of the leaf, but form circular loops and join together inside the outer leaf margins. This feature makes the plants very easy to identify in all stages of growth. When fireweed first emerges in early spring, it can closely resemble several highly toxic members of the lily family, however, it is easily identified by its unique leaf vein structure.