Yes, it is considered highly invasive in many wetland areas outside its native range.

Does it need a lot of water?

It thrives in very moist to wet soil and is often found near streams or ponds.

Plant guide

Great Willowherb.

Epilobium hirsutum

Pronounced eh-pi-LOH-bee-um HER-soo-tum

Also known as Codlins And Cream, Great Hairy Willowherb, Great Willowherb, hairy willowherb

The Great Willowherb is a vigorous perennial often found near water. It produces tall, hairy stems topped with vibrant pink flowers. It is a fantastic choice for naturalizing in damp areas of your garden.

At a glance

Care level: Easy
Plant type: Perennial
Light: Full sun to partial shade
Indoor light: bright-indirect
Water: Every 1 to 3 days
Mature size: Up to 150 cm tall
Growth rate: fast
Hardiness: USDA 4 to 9
Bloom time: Mid summer to early autumn

Care

Keep the soil consistently moist as this plant thrives in wet conditions. Watch for aphids during the growing season and prune back dead stems in late autumn. It spreads readily, so consider its location carefully to prevent it from taking over.

Watering: Keep the soil constantly damp, never allowing it to dry out completely.
Feeding: Apply a balanced liquid fertilizer once during the spring if the soil is poor.
Pruning: Cut the plant back to the ground in late autumn after the foliage dies off.
Repotting: Repot only if the plant becomes root bound in a container.
Soil: Moist, heavy, or boggy soil
Soil pH: Neutral to slightly alkaline
Temperature: -20 to 30°C
Humidity: 60 to 90%
Drought tolerance: low
Lifespan: Perennial, typically 5 to 10 years.
Deer and rabbits: moderate

Signs it needs repotting

Roots growing out of the drainage holes.
Water sitting on the surface of the soil for too long.
The plant stops growing despite regular watering.

Safety

People: It is not considered toxic to humans.
Pets: This plant is not known to be toxic to cats or dogs.
Children: The fine hairs on the plant can be irritating if handled, so it is best to keep small children from playing with the foliage.
Contact allergens: The fine hairs on the stems and leaves may cause mild skin irritation in sensitive individuals.
Airborne allergens: The wind dispersed seeds have fine, silky tufts that can be a minor respiratory irritant if inhaled in large quantities.
Edibility: While young shoots are sometimes consumed, they can be tough and lack significant culinary value.

How to identify it

Tall, hairy, branched stems
Opposite, lance shaped, serrated leaves
Large, four petaled pink flowers
Long, slender, pod like seed capsules

Height: 0.8 to 1.5m
Spread: 0.45 to 0.9m
Leaves: green, deciduous
Flowers: pink, magenta, 2 to 3cm

Common problems

Rust fungus — Appears as orange or brown pustules on the undersides of leaves during humid weather.
Aphids — Small insects that cluster on new growth and suck plant sap.

Growing it

Propagation: division, seed, cuttings
When to plant: spring, autumn
Overwintering: The foliage dies back to the ground in winter. You can cut the dead stems down to the base in late autumn or early spring.
In containers: It is not recommended for containers because it spreads aggressively and requires constant moisture.

Rhizome Division

1. Dig up a section of the root mass in early spring.
2. Use a sharp spade to divide the rhizomes into smaller pieces.
3. Replant the divisions immediately into moist soil.

Plant it in contained areas or large sites where its aggressive spreading habit will not overwhelm smaller, delicate species.

Grows well with

Purple Loosestrife — They share similar moisture requirements in wetland settings.
Meadowsweet — This plant provides a nice textural contrast in damp meadow plantings.

Keep away from

Native wetland grasses — It can easily outcompete and crowd out slower growing native grasses.

Similar species

Fireweed — It has similar flower shapes but lacks the hairy foliage and prefers drier soil.

Science

Family: Onagraceae
Genus: Epilobium
Order: Myrtales
Class: Magnoliopsida
Native range: Europe, Asia, and parts of North Africa.
Conservation: It is not of conservation concern and is considered an invasive weed in many parts of North America.

It colonizes damp ground and disturbed wetlands by spreading rapidly through its extensive root system.

Value to wildlife: nectar source, larval host plant
Pollinators: bees, moths, butterflies
Uses: wetland restoration, pollinator gardens, wildlife habitat

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 2/9
Soil reaction: 6/9
Light: 7/9
Temperature: 5/9
Moisture: 8/9
Nutrients: 6/9

Taxonomy resolved against GBIF.

Questions people ask

Is it invasive?: Yes, it is considered highly invasive in many wetland areas outside its native range.
Does it need a lot of water?: It thrives in very moist to wet soil and is often found near streams or ponds.

Where the name comes from

The name Epilobium comes from Greek words meaning upon a pod, referring to the flower position on the seed capsule. Hirsutum refers to the hairy texture of the leaves and stems.

Good to know

It spreads aggressively through both seeds and underground rhizomes.
The plant is highly adaptable to various water levels.
It is a member of the evening primrose family.

Is your great willowherb looking unwell?

This page is a general guide. Pocket Botanist diagnoses problems from a photo of your actual plant, works out watering for your light and conditions, and reminds you when care is due.

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This guide was generated with AI and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.