Parthenium hysterophorus: Congress grass

Family: Asteraceae
Common name: Congress grass, Carrot grass, Famine weed, Whitetop weed

Parthenium is a weed that grows in open areas, roadsides, hillsides and even in agricultural land, affecting productivity of other crops. It is extremely well-adapted to the Indian climate and grows abundantly in most states. It was said to have been introduced in India through contaminated imported wheat, but the plant is now considered invasive species all over the world.

The name ‘famine weed’ comes from the capability of this plant to invade agricultural land, causing drastic loss of yield. Contact with Parthenium can cause skin allergies in humans and cattle. The leaves are toxic due to a chemical called parthenin; and so farmers are careful to ensure that no parthenium leaves are mixed in green fodder given to cattle.

The plant grows to a height of 1-2 meters, with carrot-leaf like foliage, and small white flowers in clusters, that stand tall above the plant so that the pollen grains can be carried easily by wind. These plants produce 3000 million pollen grains per square meter, during their peak blooming season, which is carried long distances by the wind, causing pollen allergies in human beings. These may include wheezing, skin allergies, swelling of the eyes, runny nose, itchiness etc.

Most countries have been trying to curb the spread of this plant, mostly by biocontrol methods like the introduction of beetles that feed on the flowers and buds of Parthenium. Recently, scientists have discovered some medicinal properties for this plant, in treatment of urinary tract infections, malaria, skin inflammation and rheumatic pain.

Propagation is through seeds.

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