Ambrosia artemisiifolia

Did You Know?

• The species name artemisiifolia refers to the leaves' resemblance to those of Artemisia.
• Common ragweed is also called American wormwood, bitterweed, blackweed, carrot weed, hay fever weed, Roman wormwood, short ragweed, stammerwort, stickweed, and tassel weed.

Distribution

This plant is native to North America across Canada, the eastern and central United States, the Great Plains, and Alaska; the Caribbean on Cuba, Hispaniola, and Jamaica; and South America in the southern bioregion (Argentina, Chile, Paraguay, Uruguay), the western bioregion (Bolivia, Peru), and Brazil. It is the most widespread species of the genus in North America. Its distribution in Europe is expected to expand northwards due to climate change.

Description

Ambrosia artemisiifolia is an annual that emerges in late spring and propagates by seed. It is much-branched, growing up to 70 cm tall, with pinnately divided soft, hairy leaves 3–12 cm long. Its bloom period in North America is July to October, and its wind-dispersed pollen is a strong allergen for people with hay fever. It produces 2–4 mm obconic green to brown fruit and sets seed in later summer or autumn.

The seeds persist into winter, are numerous and rich in oil, and are eaten by songbirds and upland game birds. This species hosts several insect-induced galls, including those from Aceria ambrosiae, Asphondylia ambrosiae, Aulacidea ambrosiaecola (ragweed stem gall wasp), Epiblema strenuana, Neolasioptera ambrosiae, Procecidochares gibba, and Rhopalomyia ambrosiae. It is a widespread invasive species that has naturalized in Europe, temperate Asia and the Indian subcontinent, temperate northern and southern Africa and Macaronesia, Oceania (Australia, New Zealand, Hawaii), and Southwestern North America.

It is a very competitive weed that can cause up to 30 percent yield loss in soybeans; night tillage reduces emergence by about 45 percent, and small grains overseeded with clover suppress it.

Chemical composition, and uses

Three sesquiterpene lactones—psilostachyin A, psilostachyin B, and psilostachyin C—have been isolated from the aerial parts; all show some molluscicidal activity against the snail Oncomelania hupensis. Native American tribes including the Cherokee, Lakota, Iroquois, Dakota, and Delaware have used it medicinally. The Otoe tribe applied bruised leaves to scarified abdomens for nausea, and the Houma tribe made a tea from boiled roots for menstruation pain. It is also used in phytoremediation to remove heavy metals like lead from contaminated soil.