ageratum
     n 1: rhizomatous plant of central and southeastern United States
          and West Indies having large showy heads of clear blue
          flowers; sometimes placed in genus Eupatorium [syn: {mistflower},
           {mist-flower}, {Conoclinium coelestinum}, {Eupatorium  coelestinum}]
     2: any plant of the genus Ageratum having opposite leaves and
        small heads of blue or white flowers