Scientific Name: Ambrosia artemisiifolia L.
Other Names: Hay-fever weed, bitterweed, wild tansy, annual ragweed, and blackweed.
Life Cycle: summer annual
General Description: Erect, branched plant with pinnatifid leaves.
Seedlings: Hypocotyls are spotted or entirely purple. Cotyledons are thick, dark green, and spatulate in shape. First true leaves are opposite, becoming alternate at the fourth node. Young leaves are deeply cleft and have slightly pointed lobes.
True Leaves and Stem: Leaves are hairy to nearly smooth, and compound (pinnatifid). Stems have long rough hairs.
Roots: Shallow fiberous.
Flower and Fruit: Flowers produce large amounts of pollen. Flowers are small, green, inconspicuous, and found on terminal branches. Fruits have several longitudinal ridges ending in short spines (similar to a crown). Survival of seeds has been noted to last 80 years.