Epilobium angustifolium

Fireweed or (mainly in Britain) Rosebay Willowherb (Epilobium angustifolium) 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.

Some botanists distinguish the species from other willowherbs into either of the genera Chamaenerion or Chamerion, on the basis of its spiral (rather than opposite or whorled) leaf arrangement, but this feature (which occurs also to a greater or lesser extent in some other willowherbs) is not of marked taxonomic significance.

This herb is often abundant in wet calcareous to slightly acidic soils in open fields, pastures, and particularly burned-over lands; the name Fireweed derives from the species' abundance as a coloniser on burnt sites after forest fires.

Its tendency to quickly colonize open areas with little competition, such as sites of forest fires and forest clearings, makes it a clear example of a pioneer species.

Plants grow and flower as long as there is open space and plenty of light, as trees and brush grow larger the plants die out, but the seeds remain viable in the soil seed bank for many years, when a new fire or other disturbance occurs that opens up the ground to light again the seeds germinate.

Some areas with heavy seed counts in the soil, after burning, can be covered with pure dense stands of this species and when in flower the landscape is turned into fields of color.

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 relative species, Dwarf Fireweed (Epilobium latifolium), grows to 0.3–0.6 m tall.

The radially symmetrical 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 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.



Source: http://en.wikipedia.org/wiki/Fireweed


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