Desmodium cuspidatum (Muhl. ex Willd.) DC. ex G.Don
Family: Fabaceae
bracted tick-trefoil, large-bracted tick-trefoil
Desmodium cuspidatum image
from USDA Plants website  
Etymology: Desmodium: Greek meaning "long branch or chain," probably from the shape and the way the seedpods attach
Plants: erect, perennial, to 6 1/2 ' tall forb; stout, leafy stems
Leaves: 3-parted, leaflets bright green on top and paler below
Flowers: pink, 5-parted, 1/4"-1/2" long, stalked; inflorescence a spike-like cluster with few or no branches; blooms July-Aug.
Fruits: flat pod covered with hooked hairs and divided into triangular segments
Habitat: dry; woods, thickets
Conservation Status: Native