Eutrochium purpureum aka Gravelroot

Eutrochium purpureum is a tall perennial in the aster family. Gardeners know it as Joe-Pye weed or sweet Joe-Pye weed. Its native range spans southeast Canada and central and eastern America. It grows on wooded slopes, woodland edges, and shaded riverbanks. It also occurs in moist prairies, thickets, and roadside ground. The plant forms upright clumps and loses its leaves each year.

Garden plants reach 4–7 feet [1.22–2.13 metres] in height. They spread about 2–4 feet [0.61–1.22 metres] across. RHS gives a taller upper limit of 8.2 feet [2.5 metres]. Shallow, fibrous roots support thick, firm stems. The smooth green stems have purple marks at leaf nodes. Lance-shaped leaves grow in rings of three or four. Their edges have coarse teeth, and their upper faces feel smooth. The paler undersides may carry fine hairs. Leaves can reach 1 foot [0.30 metres] long.

Small pink-purple flowers open from July through September. Each tubular bloom has a scent like vanilla. They gather at stem tips in broad, rounded flower clusters. These can span 1–1.5 feet [0.30–0.46 metres] across. Bees, butterflies, moths, and skippers visit the blooms. Caterpillars feed on the leaves, and birds eat the seeds. Fruits appear from August to November. Each small cypsela has a tuft of hairs. Wind carries them away, while seed heads can remain through winter.

Grow this plant in sun or partial shade. It needs moist soil and does not cope with dry ground. Rich soil with humus suits it, but it also tolerates clay. Good drainage helps, though the plant accepts brief wet spells. RHS lists sand, loam, chalk, and clay as suitable soils. It also accepts acid, neutral, or alkaline conditions. Missouri Botanical Garden lists USDA zones 4–9; RHS rates it H7. Cut the stems down after the season or in late winter. Seeds, stem cuttings, and division offer ways to raise new plants. Seed germination can be poor, even after cold, moist treatment.

Its height suits the back of borders and broad group plantings. It also fits cottage gardens, meadows, woodland edges, and pond margins. Rain gardens and wildlife gardens offer other uses. Deer tend to leave it alone. Pests and diseases cause few problems, though mildew and rust can occur. Dry soil can scorch the leaves. Too little light can leave stems weak and prone to falling. The supplied sources do not establish human edibility or toxicity.