Parthenium Hysterophorus & X28;Parthenium Weed& X29; Stock Photo

Parthenium hysterophorus is a much-branched, short-lived & x28;annual& x29;, upright & x28;erect& x29; herbaceous plant that forms a basal rosette of leaves during the early stage of growth. It usually grows 0.5-1.5 m tall, but can occasionally reach up to 2 m or more in height. Mature stems are greenish and longitudinally grooved, covered in small stiff hairs & x28;hirsute& x29;, and become much branched at maturity. The alternately arrangedleaves are simple with stalks & x28;petioles& x29; up to 2 cm long and form a basalrosette during the early stages of growth. The lower leaves are relatively large & x28;3-30 cm long and 2-12 cm wide& x29; and are deeply divided & x28;bi-pinnatifid or bi-pinnatisect& x29;. Leaves on the upper branches decrease in size and are also less divided than the lower leaves. The undersides of the leaves, and to a lesser degree their upper surfaces, are covered with short, stiff hairs that lie close to the surface & x28;they are appressed pubescent& x29;.