Flower:

1 to 3 stalked flower heads at the end of branching stems and arising from leaf axils. The flower center is broad, ½ to ¾ inch across, made up of tiny dull light yellow disk flowers with 4 or 5 lobes. Ray flowers (petals) are uncommon, though 1 to 5 rays, often short and stubby, may be observed. Inner bracts are relatively inconspicuous.

The head is surrounded, almost rosette-like, by 5 to 13 leafy outer bracts that are variable in size, ¼ to 2½ inches long, to 2/3 inch wide, broad lance-elliptic that are typically hairy near the base and may be sparsely hairy around the edges.

Leaves and stems:

Leaves are 2 to 4 inches long, ¾ to 1½ inches wide, opposite, simple, narrow to broad lance-elliptic, usually toothed, sometimes untoothed, pointed at the tip, stalkess or tapering at the base to a (more or less) winged stalk. Occasionally a lower leaf may have one to a few lobes towards the base. Stems are erect and branched, green or yellow in color. Both stems and leaves usually smooth but may be finely hairy.

Fruit:

Flower heads turn into round seed heads, covered in flat, dark brown seeds.

Seeds are 1/3 to ½ inch long, usually with 3 barbed awns, the middle awn shorter than the side awns.

Notes:

Three-lobe Beggarticks often goes by Latin name Bidens comosa but the accepted name in Minnesota is Bidens tripartita. There are several species of Bidens with similar flowers, but they are not so difficult to tell apart once you know the secret. Purple-stem Beggarticks (Bidens connata) also has opposite leaves that are mostly simple, but a smaller flower head that is more orange than yellow, narrower leafy bracts, and 4-angled seeds that usually have 2 to 4 awns. Devil's Beggarticks (Bidens frondosa) has leaves compound in 3s or 5s and seed with only 2 awns. Big Devil's Beggarticks (Bidens vulgata) has numerous bracts that are densely and coarsely hairy, leaves  compound in 3s or 5s, and 2-awned seeds. While several references state Three-lobe Beggarticks can reach heights of 5 feet, I have not personally seen it more than 2 feet tall.