The reddish stems of this herbaceous perennial are usually simple, erect, smooth, 0.5–2 metres (1+1⁄2–6+1⁄2 feet) high with scattered alternate leaves.

[3]: NQ The inflorescence is a symmetrical terminal raceme that blooms progressively from bottom to top, producing a gracefully tapered shape.

Fireweed is often abundant in wet calcareous to slightly acidic soils in open fields, pastures, and particularly burned-over lands.

Fireweed reaches its average peak colonization after five years and then begins to be replaced as trees and brush grow larger.

Some areas with heavy seed counts in the soil can, after burning, be covered with pure dense stands of this species and when in flower the landscape is turned into fields of color.

[citation needed] In Britain the plant was considered a rare species in the 18th century,[8] and one confined to a few locations with damp, gravelly soils.

The plant's rise from local rarity to widespread abundance seems to have occurred at the same time as the expansion of the railway network and the associated soil disturbance.

Fireweed is also a medicine of the Upper Inlet Dena'ina, who treat pus-filled boils or cuts by placing a piece of the raw stem on the afflicted area.

Most fireweed honey is produced in locations in cool climates, such as the Pacific Northwest in the United States and Scandinavian countries in Europe.

[23] Fireweed's natural variation in ploidy has prompted its use in scientific studies of the possible effects of polyploidy on adaptive potential[24] and species diversification.

[28] It is also able to quickly establish a root system for reproduction and through this can prevent mass wasting and erosion events from occurring on burned or logged hillsides.

Disturbed and burned over lands are generally unpleasant to look at and pose a risk to habitats and nearby communities because of their susceptibility to mass wasting events.

Fireweed can quickly establish itself across the landscape and prevent further damage, while providing a blanket of vegetation for recovering fauna to create new habitats in and for pollinators to foster the re-establishment of a diverse set of flora.

[29] In The Fellowship of the Ring (1954), J. R. R. Tolkien lists fireweed as one of the flowering plants returning to the site of a bonfire inside the Old Forest.

[31] Another children's novel, A Reflection of Rachel features a protagonist attempting to restore an old garden that used "Rose Pink Willow Herb" as an ornamental plant and mentions its notoriety for growing on abandoned bomb sites.

"[33] Rosebay Willowherb was voted the county flower of London in 2002 following a poll by the wild plant conservation charity Plantlife.