Eupatorium cannabinum
hemp agrimony
Europe, North Africa, and western Asia
Overview
Eupatorium cannabinum is an upright, clump-forming perennial reaching 3-5 feet (90-150 cm) tall and 2-3 feet (60-90 cm) wide, with reddish, branching stems. The leaves are opposite and palmately divided into three to five toothed, lance-shaped lobes 2-4 inches (5-10 cm) long, resembling those of hemp, which gives the plant its common name. From July to September, dense, flat-topped clusters of small pink to mauve flower heads open at the stem tips, each head holding five to six tubular florets. The flowers draw large numbers of butterflies, bees, and hoverflies. Seeds are small achenes tipped with a pappus of hairs and carried by wind. Native to Europe, North Africa, and western Asia, E. cannabinum grows in damp meadows, ditches, fen margins, and along streams and woodland edges. It spreads by short rhizomes and self-seeds freely, which can make it weedy in moist ground. The plant tolerates a wide pH range and seasonal wetness, dies back to the ground in winter, and regrows each spring. It is hardy to USDA zone 5.
Native Range
Native to Europe, North Africa, and western and central Asia. Naturalized in parts of North America, where it grows in wet meadows, ditches, and along watercourses.Suggested Uses
Grown in rain gardens, pond and stream margins, wet meadows, and wildlife borders. Spaced 24-36 inches (60-90 cm) apart, it forms a tall back-of-border clump that supplies late-season nectar.How to Identify
Appearance
Size & Dimensions
Height3' - 5'
Width/Spread2' - 3'
Reaches mature size in approximately 2 years
Bloom Information
Flowers open from July to September in dense, flat-topped clusters of pink to mauve heads. Bloom lasts six to eight weeks and overlaps the late-summer nectar gap. Seed heads with tufted achenes follow and persist into autumn.
Detailed Descriptions
Flower Description
Pink to mauveFoliage Description
GreenGrowing Conditions
Sun Requirements
Requires 4-8 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
Care & Maintenance
Care Guide
Eupatorium cannabinum grows in full sun to partial shade in moist to wet soil across a pH of 5.5 to 7.5, and tolerates clay, loam, and seasonally flooded ground. It needs steady moisture and wilts in prolonged drought. The plant is hardy to USDA zone 5 and dies back to the ground each winter, resprouting in spring. It self-seeds and spreads by rhizomes, so removing spent heads before seed drop limits its spread. Powdery mildew can appear on crowded plants in dry spells. No fertilizer is needed in fertile, moist soil.Pruning
Cut the dead stems to the ground in late winter or early spring before new growth. Removing the flower heads after bloom reduces self-seeding. Plants can be cut back by half in early summer to limit height, which delays flowering.Pruning Schedule
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winterearly spring