CSIR-NEERI Biodiversity Portal

Congress Grass

Parthenium hysterophorus L.

Botanical name	: Parthenium hysterophorus.
Common Name	: Congress grass
Family	: Asteraceae
Synonym	: Parthenium lobatum Buckley
About	: Parthenium hysterophorus is a much-branched, short-lived (annual), upright (erect) herbaceous plant that forms alternately arranged leaves simple with stalks (petioles) up to 2 cm long and form a basal rosette during the early stages of growth. The lower leaves are relatively large (3-30 cm long and 2-12 cm wide) and are deeply divided .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 (hirsute). Numerous small flower-heads (capitula) are arranged in clusters at the tips of the branches. These flower-heads (4-5 mm across) are white or cream in colour and have five tiny 'petals' (ray florets) 0.3-1 mm long. They also have numerous (12-60) tiny tubular florets in the centre and are surrounded by two rows of small green bracts ( involucres) .Flowering can occur at any time of the year, but is most common during the rainy seasons. Five small 'seeds' (achenes) are usually produced in each flower-head (capitulum). It is native of West Indies and America. But found almost in all over India. It causes health hazards to human but is used in traditional medicines.