1 / 10

Epilobium hirsutum

great willowherb

Onagraceae

Europe, temperate Asia, North Africa

Attracts Pollinators Attracts Butterflies

SunFull Sun – Part Shade

WaterHigh

HardinessZones 5–9

Overview

Epilobium hirsutum is a tall, rhizomatous perennial in the evening-primrose family, growing 3 to 6 feet (0.9-1.8 m) tall on stout, softly hairy, branched stems. The lance-shaped leaves are 2.5-5 inches (6-12 cm) long, opposite below and alternate above, toothed, stalkless, and clasping the stem, with soft hairs over the whole plant. From midsummer it bears bright rosy-purple to pink flowers about 1 inch (2.5 cm) across, each with four notched petals and a prominent white, four-lobed cross-shaped stigma. The flowers give way to long, narrow seed capsules that split to release many seeds, each carried on a tuft of white silky hairs. The plant spreads by creeping rhizomes and wind-borne seed into dense stands along ditches, riverbanks, marshes, and damp waste ground. It colonizes wet ground quickly and is considered invasive in parts of North America. The foliage dies back to the rhizome each winter, and the dry stems persist.

Native Range

Native to Europe, temperate Asia, and North Africa, growing along rivers, ditches, marshes, fens, and damp disturbed ground. It has naturalized in North America, where it spreads in wetlands and is treated as invasive in some regions.

Suggested Uses

Used in pond margins, bog gardens, and damp wildflower plantings for its summer flowers and pollinator value, spaced 18-24 inches (45-60 cm) apart. Its spread suits large, contained wet areas rather than small borders. The flowers draw bees, hoverflies, and moths, and the seeds feed birds.

How to Identify

Recognized by tall, softly hairy stems, toothed clasping leaves, and rosy-purple four-petaled flowers with notched petals and a white, four-lobed cross-shaped stigma. The long, slender seed capsules split to release plumed seed. The dense soft hairs separate it from the smoother willowherbs and from Chamerion angustifolium, which has unnotched petals.

Appearance

Size & Dimensions

Height3' - 6'

Width/Spread1'6" - 3'

Colors

Flower Colors

purple

pink

Foliage Colors

green

Bloom Information

Bloom Period

~14 weeks

Summer Fall

Rosy-purple flowers open from June or July through September, a few opening at a time up the stems. Each flower lasts a day or two and the plant blooms over many weeks. Slender capsules follow and shed plumed seed from late summer into autumn.

Detailed Descriptions

Flower Description

Rosy-purple to pink

Foliage Description

Green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 5-12 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.5(Neutral)

357912

Soil Types

clay loam silt peat

Drainagewet

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Time to Maturity

2-3 years to full size

Care & Maintenance

Care Guide

Grows in full sun to part shade on wet to moist, fertile soil and tolerates standing water, heavy clay, and a wide pH range. It needs reliable moisture and grows poorly on dry sites. Plants are hardy to about -20F (-29C) in zones 5-9 and die back to the rhizome each winter. The creeping rhizomes and abundant plumed seed let it spread fast, so it can overrun damp borders and wild ponds. Cutting before seed set and lifting rhizome pieces help keep it in check. No feeding is needed on moist, fertile ground.

Pruning

Cutting flowering stems back before the capsules ripen limits the spread of plumed seed. Spent stems can be cut to the ground in late autumn or early spring. Lifting and dividing the rhizomes in spring both renews and contains the clump.