Pollen Type: Weed
Cross-Reactivity: Short Ragweed, Western Ragweed
HS Allergy Extract: Ragweed, Giant
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.