Cotyledons. Key characteristics: common sunflower cotyledons are much shorter and spatula-shaped (left) compared to the longer and nearly linear-shaped cotyledons of common cocklebur (right).
Seedling. Key characteristics: first true leaves are opposite and more longer than narrow; three prominent veins become apparent.
Foliage. Key characteristics: as the plant develops, leaves become heart-shaped and contain three major veins.
Flower and infested corn crop.
Seed. Seed are covered with black, gray and brown hairs imparting a mottled appearance. They are tooth-shaped and range in length from 5.0 to 8.0 mm.
Life cycle: summer annual.