Hemp Agrimony: What It Looks Like, Where It Grows, Growing in a Damp Bed and a Toxicity Warning

In brief: Hemp agrimony (Eupatorium cannabinum) is a tall perennial herb of damp habitats with pink to purplish corymbs of flowers that attract butterflies in summer. In the garden it needs damp soil and sun to partial shade. It is not used internally; it may be risky for the liver.

Hemp agrimony is a tall perennial that in summer covers damp meadows and stream banks with pink corymbs of flowers. Its flowers are popular with insects, especially butterflies and bees, and so it suits natural and wild gardens. It got its Czech name (konopáč, "hemp-like") from its leaves, which resemble hemp leaves in shape but have nothing to do with hemp.

This article explains how to recognise hemp agrimony, where it thrives and how to grow it. We do not describe any health use here, and we point out its risks.

What hemp agrimony looks like

Thanks to its height and large inflorescences, hemp agrimony stands out at the back of a bed. It is interesting even after flowering, when dew sparkles on it on a damp morning.

Where hemp agrimony grows and what it needs

In the wild it grows on water banks, damp meadows and woodland edges. In the garden it likes damp to wetter, rich soil and sun to partial shade. In dry conditions the plant suffers, dries up and loses its flowers. In the garden it is ideal by a pond, a stream or in a place with a higher water table.

Planting and sowing

Hemp agrimony is propagated by seeds and by division. The seeds are tiny and need light to germinate, so they are only pressed lightly onto the surface of damp substrate. Sow early in spring, or outdoors in autumn. Young plants are planted out after the last frosts at a spacing of 50–60 cm, so that they have enough room.

1. Choose a damp, sunny or partially shaded spot with humus-rich soil.
2. Loosen the soil and work in compost.
3. Plant the seedlings at a spacing of 50–60 cm and water well.
4. Spread mulch around the plants, which keeps moisture in.
5. Water regularly in dry weather.

Care during the year

The main care is watering. In a dry summer water generously and regularly. Feeding with compost in spring is enough. Taller plants may flop; support them in an exposed spot. After flowering you can cut off the spent flower heads, or leave them over winter for birds and for decoration. Cut back the dried foliage in spring just above the ground.

Diseases and pests

Hemp agrimony tends to be fairly healthy. In hot and dry periods powdery mildew may appear on the leaves, which you recognise by a whitish coating. Then water the plant at the roots and limit feeding. Young shoots in spring are sometimes nibbled by slugs, so watch the plants after planting. The best prevention is the right position, airiness and regular watering.

What it suits in the garden

Hemp agrimony suits wild beds, the surroundings of ponds, the edge of a stream or wetland, and gardens focused on insects. It is a specimen perennial, but stands out better in a group of three to five plants. It combines well with yellow flowers, for example with ox-eye daisies, rudbeckias or hawkweeds, which go well with the pink colour. Allow for the fact that the plants are tall, so put them in the back part of the bed.

When choosing neighbours, take care that moisture-loving species do not resemble overly lush weeds that would shade the hemp agrimony. Hemp agrimony is a good competitor, but in the first year it needs free space and regular weeding.

Overwintering and spring work

Hemp agrimony is a perennial plant and overwinters in the ground without protection. The above-ground part dies back in autumn. You can cut it back only in spring, because dried stems provide shelter for insects and decorate the bed in winter. In spring, when the ground thaws, remove the old stems just above the ground, work in compost and, when establishing new plantings, divide the plants. A compost mulch keeps moisture in during the following summer.

Care plan

Propagation and rejuvenation

Older clumps are divided in spring, before the plant grows. Dig up the clump, divide it into parts with roots and plant them in new places. The plant also likes to self-seed. If you do not want it to spread, cut off the flower heads before the seeds ripen.

Hemp agrimony in the garden for beneficial insects

In the open countryside hemp agrimony is among the important sources of nectar for butterflies and other insects. In the garden you can combine it with other moisture-loving species, for example irises, meadowsweet, thistles or loosestrife. Together they create a colourful bed for pollinators at a time when other plants are already finishing flowering. You can find further advice on natural plantings in the article Don't be a dunce, get the right flower pot.

Most common mistakes in growing

• Dry position. The plant dries up and does not flower.
• Shade. Legginess and weak flowering.
• Planting too close. Dampness and density promote fungal leaf diseases.
• Neglected self-seeding. Plants crowd the surrounding plantings.
• Unsuitable use. Do not prepare infusions from unverified plants.

Warning: toxicity and safety

• The plant is among the species that contain substances considered risky for the liver. Do not use it internally, and we do not recommend home teas, infusions or tinctures.
• If you have children or pets, plant it where they will not nibble it.
• Wash your hands after handling the plant. In some people, plants of the daisy family can cause a skin reaction.
• In the wild collect only what you know safely, and do not destroy the places where it occurs.

Frequently asked questions

What is hemp agrimony?

A tall perennial herb of damp places with pink flowers; the best known is Eupatorium cannabinum.

When does hemp agrimony flower?

From July to September. The flowers are popular with butterflies and bees.

What position does hemp agrimony need?

Sun to partial shade and damp soil, ideally by water. It suffers in dry conditions.

Is hemp agrimony poisonous?

It contains substances considered risky for the liver, so it is not used internally. For garden growing it is safe, as long as children and animals do not nibble it.

How is hemp agrimony propagated?

By dividing clumps in spring or by seeds sown on the surface of the substrate.

Sources

• Hemp agrimony – Wikipedia
• Daisy family – Wikipedia

Updated: 5 October 2026