American Willowherb
Epilobium ciliatum · Herbaceous perennial (Non-woody)
Plant Family
Onagraceae
Tree Category
Wildflower / Herbaceous Weedy Perennial
Variety / Cultivar
Subspecies ciliatum
Hardiness Zones
USDA Zones 3 through 10; highly adaptable to temperate and subarctic climates.
About This Tree
While not a tree, this is an upright, often multi-branched herbaceous plant reaching up to 1.5 meters. It features small, four-petaled pink flowers at the tips of long, slender seed pods (elongated ovaries) that split to release wind-borne seeds.
Leaf Characteristics
Opposite arrangement lower on the stem, becoming alternate higher up. Leaves are lanceolate to ovate, 3-10 cm long, with finely serrated margins and visible veins.
Bark Characteristics
No true bark; stems are green to reddish-purple, often covered in fine glandular hairs (ciliate) especially in the upper portions.
Growing Information
Origin Region
Native to North America, naturalized in Europe, Asia, and Australasia
Growing Season
Flowering occurs mid to late summer (July–September) with seed dispersal in autumn
Sunlight & Water Needs
Full sun to partial shade; prefers moist to wet soils but highly adaptable to dry disturbed sites.
Mature Size
Mature height of 0.3 to 1.5 meters; spread of 0.3 to 0.6 meters; fast growth rate; annual or short-lived perennial.
Special Characteristics
Highly prolific seeder; colonizes disturbed ground, gardens, and wetlands; long, linear seed capsules are distinctive.
Wildlife & Ecology
Attracts small bees, hoverflies, and butterflies for nectar; seeds are dispersed by wind via silky white hairs; provides ground cover for small invertebrates.