Ageratina altissima  (Eupatorium rugosum) white snakeroot Asteraceae EURU; Bx, bg, br, bz, pb, sd, sf, up, vc, wv (Yost et al. 1991); NY, bl (Stalter and Tang 2002), ct, hb, iw, rr; Q, a, cu, f, j, u, wl; K, p; R, ah, c, a, cg, fk, gb, js, jw, lp, pr, sv, t;

   

Eupatorium rugosum.www.muhlenberg.edu. C. Friedl, Muhlenberg College

Eupatorium rugosum.www.muhlenberg.edu. C. Friedl, Muhlenberg College (Accessed 4/2014).

Ageratina altissima is a perennial herb, 30-150 cm tall, stems 1-3 together, from a knotty root crown, stems usually hairless below inflorescence. Plant poisonous (Kingsbury 1964). 

Leaves opposite, stalk 10-30 cm long, blade 6-18 cm long, 3-12 cm wide, rather thin, egg-shaped, tip long-pointed, margin coarsely toothed. 

Ageratina altissima close-up. By Steven Baskauf. Copyright © 2017 CC-BY-NC-SA. New England Wild Flower Society. gobotany.newenglandwild.org

Ageratina altissima close-up. By Steven Baskauf. Copyright © 2017 CC-BY-NC-SA. New England Wild Flower Society. gobotany.newenglandwild.org (Accessed 7/2017).

Flowers bright white, 12-25 per head, no rays, bracteate base 0.3-0.5 cm tall, bracts in 2 rows, sub-equal; inflorescence branched, flat-topped; blooms Aug.-Oct. 

Fruit dry, 1-seeded, 5-angled plumed achene, wind dispersed, seeds eaten by some birds (Martin et al. 1951). 

Wetland status: UPL. 

Frequency in NYC: Common. 

Origin: Native. 

Eupatorium rugosum.David Burg.Van Cortlandt Park, NYC.12:2015

Eupatorium rugosum in fruit.David Burg.Van Cortlandt Park, NYC.12:2015

Habitat: Disturbed, upland woods, along wooded margins of highways, stream corridors; shade and drought tolerant. Tolerant of urban conditions and disturbance. 

Notes: Toxic to deer, so not eaten. Formerly caused poisoning when milk from cows that had eaten E. rugosum was ingested. The toxin is a phenolic and can be lethal. (Kingsbury 1964). Also contains barium sulphate which is toxic in quantity (Yatskievych 2006).