Epilobium

Epilobium is a genus in the family Onagraceae, containing about 160-200 species of flowering plants with a worldwide distribution. They are generally abundant in the subarctic, temperate and subantarctic regions, whereas in the subtropics and tropics they are restricted to the cool montane biomes, such as the New Guinea Highlands where they are plentiful.

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. Chamerion might be distinct however, as advocated for example by Peter H. Raven who has extensively studied the willowherbs and does on the other hand merge the other segregate genera into Epilobium. Fringed Willowherb (E. ciliatum) is suspected to be a cryptic species complex; apparently these plants also commonly hybridize with their congeners.

Most species are known by the common name willowherbs; in particular those that were once separated in Boisduvalia are called spike-primroses or boisduvalias. Yet other species, namely ones that are placed in the Chamerion group, are also known as "fireweeds".