Rosebay willowherb

The tall, pretty pink flower spikes of rosebay willowherb (Chamaenerion angustifolium) are a common sight on railway banks and disturbed woodland. It is a useful nectar source for pollinators but self-seeds readily and can become a troublesome garden weed.

Rosebay willowherb
Rosebay willowherb

Quick facts

Common name Rosebay willowherb, fireweed
Botanical name Chamaenerion angustifolium
Synonyms Chamerion angustifolium, Epilobium angustifolium
Area affected Disturbed ground
Caused by Windborne seed and branching underground stems (rhizomes)
Timing Flowers June to September; treat spring to autumn

What is rosebay willowherb?

Chamaenerion angustifolium is a native perennial weed which spreads by seed and

rhizomes (underground stems) and is unsuitable in a small garden. It is found growing on waste land, scrub, rocks, woodland and also gardens where it can become a serious weed.

A white

cultivar Chamaenerion angustifolium ‘Alba’ is available as a garden plant and shows less invasive tendencies than the pink form.

Rosebay willowherb is a valuable food source for numerous species of moths and butterflies; it is also a useful nectar source for pollinators, including bees.

Bees in your garden

Bees in your garden

Butterflies in your garden

Butterflies in your garden

Moths in your garden

Moths in your garden

The white or pink flowered rosebay willowherbs may be welcomed by gardeners wishing to fill large borders, but in smaller gardens some control measures may be needed. This page looks at options for gardeners when rosebay willowherb is becoming a problem. 


Height to 1.5m (5ft) with deep pinkish-purple flowers in tall spikes from June to September. When ripe the long seed capsules split open to reveal numerous fluffy seeds.

The problem

Rosebay willowherb is quick growing and produces abundant fluffy seeds which are readily carried on the wind. The roots are long, branched and spreading and give rise to new leafy shoots producing large patches.


The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner. 

Cultural control

Cultural methods such as hoeing and forking-out are effective against this shallow-rooted weed. Opaque mulching films can also be used to suppress its growth around woody plants or on unplanted beds.

Weedkiller control

The RHS does not support the use of weedkillers and recommends that alternative control methods are used. However, we do note that when gardeners struggle to control plants with cultural methods, regulated weedkillers/pesticides for home gardeners are available for use legally. Garden centres and large retailers selling weedkillers have trained staff who can advise on suitable products for your needs.

Weeds: non-chemical control

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