Until early in the nineteenth century rosebay willowherb (Chamerion angustifolium) had a restricted distribution in the British Isles. Thereafter it became much more widespread, beside railways, in disturbed areas, woodland clearings, and on burnt ground. It also acquired a variety of local names, possibly suggesting that the plant spread faster than its name, so people invented new names for it
Rosebay willowherb’s leaves resemble those of some narrow-leaved willows (Salix spp.), leading to such names as blooming sally (i.e. flowering sallow) in Cumberland and Ireland, flowering withy in Berkshire, and blooming willie in Co. Tyrone.
Due to its ability to rapidly colonise burnt ground and bombsites rosebay willowherb acquired such names as fireweed, or, less frequently, bomb-weed ‘because it was first to grow on bombsites’, London pride, and London’s ruin. In Clydebank, West Dunbartonshire, where the plant grew in profusion on the site of the Singer Sewing Machine factory which was bombed during World War II, it was known as Singerweed.
Names which are less easy to explain include blood-vine in Hampshire, cat’s eyes in Shropshire, plum jam in Dorset, red buffer in Shropshire, and ramping molly in Craven, Yorkshire.

Adapted from: R. Vickery, Local names of rosebay willowherb, The [SLBI] Gazette, ser.2, 2: 23-4, 2005, and Garlands, Conkers & Mother-die, 2010: 114-5.

Images:  main, Trent Country Park, London Borough of Enfield, August 2015; inset, garden of Dumfries House, Ayrshire, September 2017.