Synonyms: Bee Balm | Horsemint A perennial with purple clusters of flowers appear July thru August. Rhizomatous, can be aggressive. Found in North America, east of the Rockies; floodplains, shorelines and open woodlands, moist to mesic prairies. Best in full to partial sun; moderately dry to moist, but not wet soils, tolerates sandy, clay or loam soils. Moist rich soils are best.