Giant Ragweed

Pollen Type: Weed

Cross-Reactivity: Short Ragweed, Western Ragweed

HS Allergy Extract: Ragweed, Giant

Family: Compositae

Genus/Species: Ambrosia trifida

Common Names: Giant Ragweed, Tall Ragweed, Crownweed

Distribution: Quebec to North Carolina, west to British Columbia and Colorado. The Dakotas, Nebraska, and Kansas are its western limits of dense distribution.

Locations: Giant Ragweed prefers moist regions like stream banks and flood plains. It can be a noxious invasive plant in cultivated crops. It is also common in disturbed urban areas.

Pollination Method: Wind-pollinated

Pollinating Period: Early August into late September

Description: Giant Ragweed is a coarse, abundant annual, sometimes growing 10’-15’ tall. The herbage is rough and its leaves are 3-5 cleft (although sometimes entire) on long petioles (stems). The numerous staminate (male) heads grow on the long terminal spikes. The pistillate (female) heads grow in small clusters at the base of the staminate (male) spikes. Giant Ragweed probably produces the most copious amounts of pollen of any of weed.

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