The upper surfaces of the cotyledons have a distinctive midvein. First true leaves are opposite and deeply dissected. Leaves are finely dissected and have 2 to 3 rows of lateral leaflets that are ovate to lanceolate in outline. Erect, square in cross-section, branching in the upper section, and with small tufts of hairs at the nodes. Occur in solitary heads on long stalks.
Flowers are yellow and are composed of inner disk flowers and outer ray flowers.
Flowering heads are surrounded by green bracts that are approximately 2 to 7 mm long and narrow. An achene that is approximately 8 to 18 mm long, linear in outline, and dark brown in color. Achenes have 3 to 4 spines at the apex that are pointed downward. Summer annual with leaves that are dissected 2 to 3 times and have yellow flowers. Additionally, common ragweed seedlings do not have the characteristic maroon highlights on the cotyledon and leaf undersurfaces like those of spanishneedles.