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Annual ragweed

Botanical Name:

Ambrosia artemisiifolia

Common Name:

Annual ragweed,Petite herbe à poux,Short ragweed,American Wormwood,Bitterweed,Blackweed,Carrot Weed,Common Ragweed,Hay Fever Weed,Ragweed


Ambrosia artemisiifolia is an annual plant that emerges in late spring. It propagates mainly by rhizomes, but also by seed.It is much-branched, and grows up to 70 centimetres (2.3 ft) in height. The pinnately divided soft and hairy leaves are 3–12 centimetres (1.2–4.7 in) long.Its bloom period is July to October in North America. Its pollen is wind-dispersed, and can be a strong allergen to people with hay fever.It produces 2–4 mm obconic green to brown fruit. It sets seed in later summer or autumn. Since the seeds persist into winter and are numerous and rich in oil, they are relished by songbirds and upland game birds. Invasive speciesEdit Common ragweed, Ambrosia artemisiifolia, is a widespread invasive species, and can become a noxious weed, that has naturalized in: Europe; temperate Asia and the Indian subcontinent; temperate northern and southern Africa and Macaronesia; Oceania in Australia, New Zealand, and Hawaii; and Southwestern North America in California and the Southwestern United States.Common ragweed is a very competitive weed and can produce yield losses in soybeans as high as 30 percent. Control with night tillage reduces emergence by around 45 percent. Small grains in rotation will also suppress common ragweed if they are overseeded with clover. Otherwise, the ragweed will grow and mature and produce seeds in the small grain stubble. Its wind-blown pollen is highly allergenic. Ragweed controlEdit As of 2005 several herbicides were effective against common ragweed, although resistant populations were known to exist. In 2007 several Ambrosia artemisiifolia populations were glyphosate resistant, exclusively in the USA.As of 2014 the ragweed leaf beetle, Ophraella communa, has been found south of the Alps in southern Switzerland and northern Italy. Many of the attacked plants were completely defoliated. Zygogramma suturalis was introduced to Russia, and then China, for ragweed control, with very positive initial results. SMARTER is a European interdisciplinary network of experts involved in the control of ragweed, health care professionals, aerobiologists, ecologists, economists, and atmospheric and agricultural modellers.

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Bloom Time

Summer, Jun, Jul, Aug

Plant Type

Annual, Weed, Herb



Plant Height

1-3 ft.


1-4 inch long terminal flower spikes occur and may have 2 short side spikes. The individual 1/8 inch flower is green, turns yellow-green then brown as it matures. Pollen is released late summer into fall and is carried by the wind.


Woody achene with 4-7 spine-like projections, resembling a crown. They contain numerous seeds that are viable for up to 5 years.

How to Grow


Full sun (6 or more hours of direct sunlight a day), Sun, Part Shade, Shade




Plant parts can cause skin irritation if touched.

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