GROWTH HABIT: This native annual reaches 4 feet tall.
LEAVES: Leaves are pinnately divided and are both alternate and opposite. The bottom side of the leaf has a gray appearance because of fine hairs.
STEMS: Stems and leaves are blue-green and are covered with fine hairs.
FLOWER: Flowers are found on terminal branches, which have male and female flowers in clusters with staminate flowers found above the pistillate flowers. Flowering occurs in late summer.
SEEDS: Seeds are awl-shaped with a spiny projection on one side. Seeds mature by October.
OTHER: This annual is common throughout the western U.S. causing many individuals to have hay fever. Even though it is common, it is not highly competitive in crops or rangeland. It is commonly found along ditches and in waste areas. Western ragweed (A. Psilostachya DC.) Is shorter in stature and is commonly found on rangeland and undisturbed perennial cropland.