Scientific name: Ageratina aromatica, syn. Eupatorium aromaticum
Common names: Small-leaved White Snakeroot, Wild-hoarhound, Lesser Snakeroot, Aromatic Eupatorium
Nativity: Eastern North America
Location: Sandhills Gamelands, Hoffman, NC
Date: October 23, 2016
Notes: Along with thousands of others in the 1800s, Nancy Hanks Lincoln died of “milk sickness” when she drank the milk from a cow that had eaten a close relative of this plant, white snakeroot (A. altissima). A. aromatica may or may not be less toxic than its famous relative, but it looks similar enough to avoid consuming it lest you make a mistake in identification.
The chemical involved is tremetol; you can be poisoned by having a large amount of it at once, or small amounts over a long period. Cows that have eaten the plants will begin to tremble, especially after any exertion, then die within a few days.
Having warned you, CRC World Dictionary of Medicinal and Poisonous Plants by Umberto Quattrocchi (pg. 122) lists several historic uses for A. aromatica, among them crushing the leaves to apply to bruises and sprains.