Cotyledons emerging from the soil. Key characteristics: cotyledons are large, spatula-shaped and fleshy. First true leaves appear unlobed, then develop into three major lobes.
Vegetative plants. Key characteristics: leaves develop into five major lobes and are hairy.
Flowers. Giant ragweed is a major contributor of pollen and is partly responsible for allergy problems in the late summer.
Seed. Seed are yellow-brown mottled with a large central terminal projection surrounded by several shorter projections. Length is approximately 6.0 to 10.0 mm.
Life cycle: summer annual.