rhizomatous plant of central and southeastern United States and West Indies having large showy heads of clear blue flowers; sometimes placed in genus Eupatorium
any plant of the genus Ageratum having opposite leaves and small heads of blue or white flowers
Any of the genus Ageratum of tropical American herbs, annuals and perennials, from the sunflower family Asteraceae, tribe Eupatorieae; they are sometimes used in floral displays.