Weed class: B
Year Listed: 2004
Native to: Africa, Asia and Europe
Is this Weed Toxic?:
not known to be
Why Is It a Noxious Weed?
Hairy willow-herb is a tall, attractive plant capable of escaping cultivation to form monotypic stands in natural wetland areas. Aggressive and dense growth can crowd out native or beneficial species.
How would I identify it?
Hairy willow-herb is a semi-aquatic, softly-hairy herb that ranges in height from 3 - 6 feet tall.
The showy rose-purple flowers extend from leaf axils near the top of the plant. Flowers are approximately ¾ inch across. Each flower has four sepals, four notched petals and eight stamens. Blooms occur in July and August.
The leaf arrangement is mostly opposite, and the toothed leaves are lanceolate shaped (much longer than wide, and widest below the middle).
Stems are upright, branched more near the top and covered in hairs.
Fruit Seed Description
The seeds are in long narrow capsules. Seeds have a tuft of white hairs attached.
Where does it grow?
It is found in a wide range of moist soils, including wetlands, ditch and stream banks, low fields, pastures and meadows. Please click here to see a county level distribution map of hairy willow-herb in Washington.
How Does it Reproduce?
It spreads by seeds and by rhizomes and adapts to its growing conditions. Axillary buds, found at the base of the stem, produce stolons. These stolons develop adventitious roots which pull the stolons into the ground where they develop into rhizomes.
How Do I Control It?
Small infestations may be hand dug, but care must be taken to remove as many rhizome fragments as possible. Sites must be checked for re-growth from missed root fragments. Mowing may be an option to prevent seed production but will not kill the plant.
For More Information
See our postcard for early detection information about hairy willow-herb.
See our Written Findings for more information about hairy willow-herb (Epilobium hirsutum).
WSDA Report on testing control methods of hairy willow-herb (Epilobium hirstum).
Island County NWCB Fact Sheet on hairy willow-herb
Whatcom County NWCB Fact Sheet on hairy willow-herb
King County NWCB Fact Sheet on hairy willow-herb