Great Ragweed, Ambrosia trifida, Sunflower Family (Asteraceae)
Description: A tall, rough, hairy plant with nodding heads of minute green flowers arranged in elongated clusters. Flowers: similiar to those of Common Ragweed; clusters 1-10″ (2.5-25 cm) long. Leaves: up to 8″ (20 cm) long, opposite, palmately 3-lobed. Fruit: beaked, with 4-10 short points. Height: 2-15′ (60-450 cm).
Habitat: Waste places, fields, and roadsides.
Comments: This is the giant among the Ragweeds. The pollen of this species, like that of other Ragweeds, is spread by the wind and is a principal cause of hay fever.
All flower resources taken from: Niering, William A., Olmstead, Nancy C., National Audobon Society Field Guide to North American Wildlowers. 1979, Chanticleer Press, INC.