Ageratum houstonianum Miller
A. mexicanum Sims.
Ageratum houstonianum is originating from Central America, but cultivated in tropical, subtropical and temperate regions. It is found naturalised in many warmer regions including China, India and locally in Southeast Asia (e.g. Peninsular Malaysia, Java, the Philippines, Vietnam).
A. houstonianum is an annual erect herb where at the base it sometimes creeping and rooting and up to measures 70(-90) cm tall. The stems are clothed with patent white hairs.
The leaves are subtriangular, ovate to deltoid, with a size of measuring 2-8.5(-9.5) cm x (1.5-)3-6.5(-8) cm and with cordate to truncate base.
The head is 5.5-7 mm long and with 75-100-flowered. The outermost involucral bracts are with both simple hairs and shorter glandular hairs while the inner involucral bracts are gradually tapered into an acute apex. The petal is measures 2.5-3 mm long.
The fruit is hairy.
A. houstonianum is locally common in fields, roadsides and waste places up to 1700 m altitude.