Flower:

Flowers are at the ends of branching stems and stalks that arise from the leaf axils near the top of the plant. Individual flowers are 1/8 to ¼ inch across with 5 shiny yellow rounded petals. There is a ring of yellow-tipped stamens around a bulbous yellowish center that turns bright green with maturity. The 5 green sepals are longer than the petals, covered in long hairs on the outer surface, and typically bend back away from the flower (reflexed).

Leaves and stem:

Leaves are compound in 3's, with leaflets (usually) deeply divided into 3 wedge-shaped to elliptical segments that are further lobed, notched and/or coarsely toothed. Leaflets are up to 3 inches long and 2 inches wide, becoming smaller as they ascend the stem, and are hairy. Attachment is alternate.

Leaves near the base of the plant have long stalks that sheath the stem. These often wither away early. The stem and leaf stalks are both densely covered in stiff hairs, becoming more sparsely hairy with age.

Fruit:

The flower center expands to a cylindrical seed head about ½ inch long. Seeds are tear drop shaped, flattened, with a narrow rib or wing around the edge and a mostly straight beak.

Notes:

A common wetland plant, Pennsylvania Buttercup most closely resembles Macoun's Buttercup (Ranunculus macounii), which has very similar leaves and densely hairy stems, but much larger flowers—about ½ inch across—and sepals shorter than the petals. R. macounii is also limited to the northwest counties where R. pensylvanicus is found throughout the state.