Ageratina herbacea aka Fragrant Snakeroot

Ageratina herbacea is a perennial in the daisy family, Asteraceae. Its common name is fragrant snakeroot. Its native range runs from the United States into northern Mexico. It is not native to Britain or Ireland. The older name Eupatorium herbaceum refers to the same species. In California, it grows in pinyon-juniper woodland. Records place this habitat at elevations of about 4,920–7,220 feet [1,500–2,200 metres].

Plants For A Future lists a height of 6.6 feet [2 metres]. The supplied sources give no mature spread or detailed growth shape. They also give no species-level account of its leaves or stems. Flowering runs from August to October, extending into autumn. Each flower has both male and female organs. Insects pollinate the flowers, and the plant is self-fertile. The evidence does not describe its fruit or seed heads.

For cultivation, choose soil that drains well but holds moisture. This plant prefers moist ground rather than a dry site. It can grow in sand, loam, or clay. It also accepts mildly acid, neutral, and mildly alkaline soils. Full sun and partial shade both suit it. Plants For A Future places it in USDA zones 5–9. That source also lists UK zone 6. This is not an RHS H-rating, so the two should not be confused.

A sunny woodland edge or a site with dappled shade suits its stated needs. Its late flowering season offers a reason to include it there. The sources give no further details about its landscape performance. Grow it from seed or divide plants in spring. Sow seeds in a cold frame with a light soil covering. Move seedlings into separate pots once they are large enough. Plant them outside in summer. The evidence gives no specific pest or disease warnings.

Plants For A Future lists no known edible uses. It records a traditional cold infusion for headaches and fevers. That preparation was taken as a drink or applied as a lotion. This record does not establish treatment safety or effectiveness. The source reports no known hazards, but gives no detailed toxicity assessment. It also lists no other uses and does not flag weed potential.