Rosebay Willowherb (sometimes called Fireweed) is very tall perennial. The flowers grow up in a spike, but loosely; there are four purple sepals and four irregular rosy petals. The leaves are pointed and willow-like; they grow alternately up the main stem.
Rosebay has long been a rare and colourful plant found on mountain ledges. Recently it has taken to growing in hedges and on the margin of woods and bogs, but not nearly as wildly as in Britain, where it has spread in the last fifty years through disturbed land, wood clearing and roadsides. The name 'Fireweed' was given it because it thrives on ground where fire has been.
The flowers appear from July to September.
Rosebay is found in Europe, Asia and North America.