How to Grow Hemp Agrimony
Eupatorium cannabinum
Hemp Agrimony is a tall native perennial with large clusters of fluffy pink-purple flower heads in late summer, making it the best butterfly plant for damp gardens. It thrives in moist to wet soil at pond margins, ditches, and wildflower areas. Plant in spring or autumn and leave undisturbed — it naturalises readily and spreads gently by seed and rhizome. Cut back to the ground in late autumn or early spring. Outstanding for red admirals, painted ladies, and other late-summer butterflies.
Yearly Lifecycle
Care Essentials
Rarely needed. A mulch of garden compost in spring is sufficient in poor soils. In naturally fertile or moist soils no feeding is required.
Watch For
- Powdery mildew in dry conditions
- Aphids on young shoots
Companions
Yellow Flag Iris, Purple Loosestrife, Meadowsweet
Care Requirements
Light
Full sun to partial shade
Tolerates partial shade well, especially in moist soils. Flowering is best in full sun. Ideal at the back of a damp border or pond margin.
Watering
Moist to wet soil required
Needs consistently moist or wet soil. Thrives at pond margins and in rain gardens. Will not perform well in dry soil.
Fertilizing
Minimal feeding needed
In fertile or naturally moist soils no feeding is required. A spring compost mulch is sufficient on poorer soils.
Pruning
Cut to ground in late autumn
Cut all stems to ground level after the first frosts. Alternatively leave standing for wildlife until early spring.
Growing Tips
Best butterfly plant for damp gardens
Hemp Agrimony attracts red admirals, painted ladies, comma butterflies, and many other species in late summer. Position it where you can watch from a seat.
Moist soil is essential
This plant struggles in dry soil. Site it near a pond, in a rain garden, or any reliably moist spot. It will grow in standing water at pond margins.
Leave seed heads for birds
The fluffy seed heads provide food for goldfinches and other birds. Leave them standing through early winter before cutting back.
Spacing & Planting
| Plant spacing | 75 cm |
| Row spacing | 75 cm |
| Mature height | 150 cm |
| Mature spread | 75 cm |
Tall native perennial for damp, fertile soils. Space 75 cm apart. Spreads by self-seeding and rhizomes in moist conditions. Excellent for pond margins, rain gardens, and wildflower areas.
