Epilobium is a genus of about 160-200 species of flowering plants in the family Onagraceae, native to temperate and subarctic regions of both hemispheres. Most species are known by the common name Willowherb; other names for individual species include Fireweed, Zauschneria, California-fuchsia, Codlins and cream, Spike-primrose, Hummingbird Flower, and Hummingbird Trumpet.
They are mostly herbaceous plants, either annual or perennial; a few are subshrubs. The leaves are mostly opposite or whorled, alternate in a few species, simple, and ovate to lanceolate in shape. The flowers have four petals; pink in most species, red, orange or yellow in a few. The fruit is a slender cylindrical capsule containing numerous seeds embedded in fine, soft silky fluff which disperses the seeds very effectively in the wind.
The taxonomy of the genus has varied between different botanists, but the modern trend is to include the previously-recognised genera Boisduvalia, Chamaenerion, Chamerion, Pyrogennema and Zauschneria within Epilobium.
Many species are weeds in gardens. One of the most frequently recognized members of the genus is Fireweed or Rosebay Willowherb (E. angustifolium); it rapidly colonizes burnt ground. During World War II and the bombing of London many of the derelict bomb sites were soon covered with Fireweed bringing a splash of colour to what was otherwise a very grim scene.
Epilobium species are used as food plants by the larvae of some Lepidoptera species: Double-striped Pug, The Gothic, Hebrew Character, Mouse Moth and Setaceous Hebrew Character have been recorded on Fireweed and Grey Pug, Elephant Hawk-moth and Small Angle Shades on several species.