Saturday, 12 August 2017

Rosebay willowherb (Chamaenerion angustifolium)

Image of the rosebay willowherb flowering stem
Rosebay willowherb flowers

Rosebay Willowherb (Chamaenerion angustifolium syn. Chamerion angustifolium and Epilobium angustifolium) is a perennial herbaceous plant from the Onagraceae family. Widespread in the Northern Hemisphere, it is a pioneer species and colonises disturbed ground such as newly cleared woodland or land that has been subjected to fire. It colonised bomb sites in Britain during the war and was nicknamed bombweed because of this.

Image of a stand of rosebay willowherb or fireweed
A stand of rosebay willowherb

Rosebay willowherb is known by many common names including fireweed, great willow herb, bombweed, flowering willow, French willow, Persian willow, London pride, London's ruin, singerweed, thunder flower, rose bay willow, blood vine, purple rocket, wickup, wicopy, tame withy and blooming sally. Sally is corruption of the term salix, the 'willow' genus. Rosebay willowherb has willow-like leaves.

Growing methods

The Royal Horticultural Society call it a native perennial weed which we think belies the fact that it is a native wild flower and a very useful one at that. However, do think carefully about introducing it because it has, what the experts call, a strong growth habit. It will almost certainly grow well in your garden but also in your neighbours' gardens, and their neighbours' gardens, too! It spreads by wind borne seed and vigorous shallow-rooted white branching rhizomes which can grow up to one metre a year.

Rosebay willowherb can be grown by propagating the rhizome or by sowing seed direct outside in the autumn. If sowing seed indoors, stratify before use. The plant will grow to a height of around 1.2 metres. It enjoys mildly acidic soil and tolerates a range of growing conditions including shade. It flowers from June until September with a tall spike of pale purple flowers which open gradually from the base of the racemes. Long thin seed capsules are produced which split lengthwise to expose up to 20,000 small seeds covered with white silky hairs. These fine hairs carry the seed far and wide on the wind.

Whilst it can become invasive it is not supposed to survive repeatedly being pulled up or cut down. However, we wouldn't rely on these methods to stop it spreading! Some patches we have are repeatedly scythed when the plant is around 20-30cms high and it has always grown back, usually within weeks during the summer months. These patches have also extended their growing range at the same time. In other words, the plant has continued to spread unabated. You would really have to wage quite a war on it to stop it growing simply by pulling it up and cutting it down!

Edible parts

The young shoots and young leaves can be used raw in a salad. The older leaves become tough and bitter. Cut the young plant down (at about 20-30cms) and it will sprout up again with plenty of side shoots, usually once or twice within the same season

Image of the edible leaves of young rosebay willowherb plants
Young rosebay willowherb plants

The flower stalks can be eaten raw but make sure the flowers are still in bud. The pith of the red stems can be scraped out and eaten raw. You can remove it with a finger nail on the younger plants. You'll need a sharp knife for the older stems which are very tough. It is similar to cucumber and astringent in nature but there is not much of it. The leaves can be used as a tea substitute. Green tea made from rosebay willowherb leaves taste very similar to nettle tea. The leaves can also be made into a black tea by fermenting and drying. The root can be eaten raw but we found it to be bitter. The root is fairly shallow rooted so easy to dig out of the soil but will also break easily.

The older leaves, flower stalks with buds and root can be cooked by steaming or boiling. Boiling the root may reduce or remove the bitterness.

Other uses

Downy seed hairs can be used as a fire lighter or stuffing. The fibre from the outer stem can be used to make cordage. Nettle fibres are longer and stronger. The pith when dried and powdered can be applied to hands and face for protection against cold. Rosebay willowherb is used in herbal medicine.


It can be mistaken for purple loosestrife at a distance. However, rosebay willowherb has a unique pattern on the backs of the leaves which makes identification easy. Loops of interconnected veins which don't touch the edges of the leaf, leaving a margin.

Identifying the rosebay willowherb plant by the reverse side of the leaf
The reverse of a rosebay willowherb leaf

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