This widespread southeastern species occurs north to the southern Great Lakes region. The name D. dichotomum var. ramulosum (Torr.) LeBlond was initially preferred by W but later changed to D. microcarpon. These plants are generally distinct in Ky., but some colls. appear transitional to yadkinense or dichotomum. Among these three taxa, microcarpon is distinguished by its small spikelets (ca. 1.5-1.8 mm long versus 1.8-2.5 mm), bearded lower nodes, and lower sheaths are often purplish with pale mottles between veins. A few colls. initially identified as microcarpon have been recently distinguished as D. annulum and D. lucidum; see notes under those names. There are also unverified reports from Ky. of two other wetland taxa in the dichotomum group, often treated as varieties or subspecies (M): P. nitidum Lam. and D. mattamuskeetense (Ashe) Mohl. However, those two taxa occur largely on boggy soils of the Coastal Plain or Piedmont (FNA 25; W).