Hairywillow herb is a semi-aquatic annual or perennial in the Onagraceae family native to North Africa and Eurasia. The soft wooly leaves and stems are the reason for the species name hirsutum which means hairy in Latin. This plant reaches a mature height of 6 feet tall. While they are more common in cool regions they occasionally occur as a cool-season weed in warmer areas. Hairywillow herb grows in moist soils and is often found growing in full sun in wetlands, low areas, in ditches, along roadsides, and along stream beds. Often found growing with the invasive weed purple loosestrife , it reproduces through rhizomes or by wind dispersed seed. Seedlings are small and slow to establish, but once established can be challenging to manage. This weed is becoming more prevalent in container nurseries, likely spreading in contaminated nursery crops. Inspect liners to prevent introduction. Prevent plants from going to seed. Willowherbs are not well managed by herbicides currently labeled for use. Herbicide efficacy rankings for this species are based on limited experimental data. Insects, Diseases, and Other Plant Problems: This plant is weedy, can spread aggressively, and has been marked as invasive in some regions including northern parts of the USA. Do not compost, dispose of this plant in the garbage.
Curated pairwise relationships between this plant and others in the library — who feeds
whom, who competes, who confuses the pests. Green reads as a good pairing, red as one to avoid.
No curated interactions recorded for this species yet.
Also noted by NC State
Related species the NC State Plant Toolbox flags for this plant — look-alikes to tell
apart, and plants that play a similar role in a planting. Ones we carry in the library are linked.
Full sun (6 or more hours of direct sunlight a day)
Soil drainage
Moist | Occasional Flooding | Occasionally Wet
Growth rate
Slow
Maintenance
High
Canopy layer
4 - Herbaceous
Form & Appearance
Habit / form
Erect
Leaf color
Green
Leaf type
Simple
Leaf arrangement
Opposite
Leaf shape
Lanceolate
Leaf margin
Dentate
Hairs present
Yes
Leaf detail
Mostly opposite densely hairy toothed lanceolate leaves with no petiole, they attach directly to the stem. The leaves are deeply veined.
Flower color
Pink
Flower shape
Saucer
Flower size
< 1 inch
Flower detail
The flowers are saucer shaped rose pink with white centers, resembling primrose blooms. 3/4" across, four petals with a notch at the top, four sepals, and eight stamens. They appear at the top of the plant in leaf axils. Long seed pods split open to release many wind-dispersed seeds.
Bloom time
Winter
Fruit size
1-3 inches long
Fruit detail
Dehiscent hairy thin seed pods 1 to 3 inches long. Seeds have white tufts of hair that aid in their dispersal by wind.