Tickseed sunflower is a much-branched annual or biennial. Hairless or with sparse hairs. Flowerheads daisylike, bright yellow, about 1¼ inches across, with usually 8 pointed ray florets. Bracts under flowerhead in 2 dissimilar rows; outer series spreading or reflexed, linear, not leaflike, with hairs along the margins; inner series lanceolate to narrowly ovate. Blooms August–October. Leaves opposite, pinnately (like a feather) deeply lobed or compound with 3–7 divisions, pointed, each with sharp teeth. Fruit flattened, black, with 2 needlelike awns that attach themselves to clothing and pets, thus the names “tickseed” and “beggar-ticks.”
Similar species: Eleven species of Bidens have been recorded in Missouri, plus 6 of the similar genus Coreopsis. Distinguishing among these species involves many anatomical features, including leaf characteristics, numbers of ray and disk florets, configuration of involucral bracts, and details of the fruits, right down to their barb-covered awns.