Rosebay Willowherb seeds at Wylam, Northumberland
Chamaenerion angustifolium is a perennial herbaceous flowering plant in the willowherb family Onagraceae. It is known in North America as fireweed, in some parts of Canada as great willowherb, in Britain and Ireland as rosebay willowherb. In the United Kingdom it is also known as bombweed, as a result of its rapid appearance on city bomb sites during the Blitz of World War II. It is also known by the synonyms Chamerion angustifolium and Epilobium angustifolium. It is native throughout the temperate Northern Hemisphere, including large parts of the boreal forests.