Looks lik Ageratum conyzoides to me too. Here I found good pics of Ageratum conyzoides - http://issg.org/database/image.asp?ii=1682&ic=e
I refered clear pics of Chromolaena odorata in here too- http://issg.org/database/species/ecology.asp?si=47&fr=1&sts=sss&lang=EN Regards Neha S
