Eupatorium purpureum (Gravel root). Also known as Joe Pye weed.

Head of flowers of tall plant with tubular, pinkish-purple flowers and toothed ovate leaves arranged in whorls along purplish stems. Ingestion of this plant family by sheep and cattle has been associated with 'milk sickness' in humans who ingest milk, milk products, or meat. It is marked by weakness, anorexia, vomiting, constipation, and sometimes muscular tremors.