P Parthenium hysterophorus Linn. (Asteraceae; common names in India: congress grass, sadhya, jangli dhania), a ubiquitous weed, is a native of the West Indies, and Central and Northern America. It was introduced into India unintentionally and was first seen growing around Pune, Maharashtra, in 1956, as a weed near river banks and alongside dry fields'. In 1961, it was recorded as a rare weed in Dharwar, Karnataka. By 1962, it had been the most abundant plant in the whole of Pune and in September 1964 stray plants were found in Delhi '. The weed now occupies more than five million hectares of the country. It grows on wastelands, roadsides, canal-sides, along railway lines and on uncultivated agricultural land.