Biology of Parthenium

Seedlings of Parthenium with egg-shaped leaves and covered in fine, white hairs. Older leaves become increasingly lobed and deeply divided and young plants develop into a rosette with a deep taproot system. Stems and leaves are covered in short, white hairs. Plants develop a bluish or greyish appearance. The flower heads are white and occur in clusters at the top of the plant, borne on short stalks, arising from the leaf forks. Flower heads become hard and brown as they mature. The seeds are striped grey to black and a narrow diamond shape, 2 mm long and flattened. Generally only 4 seeds develop in each head. Parthenium can germinate, flower and set seeds within four weeks. Once established, it can survive even severe drought and frost conditions.