This is widespread across southeastern states in somewhat mesic woods but it is largely absent from Appalachian regions and most of the Coastal Plain (K). Before their recent description as a species (Naczi 1999), these plants were often considered close to amphibola and grisea, or even intermediate. Naczi showed that planispicata is closer to oligocarpa, which shares the distichous arrangement of perigynia, proximal bracts with tight sheaths (versus loose), and more extensive purplish shoot bases (usually 3-9 cm versus 0-3 cm). C. planispicata differs from oligocarpa in its more elongated perigynia (L/W = usually 2.5-3.3 versus 2.1-2.6) with tapering apices (versus abruptly contracted to a more distinct beak); and its longest spikes have more perigynia (usually 7-14 versus 4-8). Its vegetative shoots are more elongated relative to fertile culms (x 1.4-4 versus x 0.9-1.4), and tend to have broader leaves (up to 3.5-6.5 mm versus 2-4.5 mm). It typically occurs on more acid loamy soils, from toe-slopes to high terraces, but the two species are often intermixed (FNA 23). C. planispicata also overlaps in habitat with digitalis (typically on more acid soils), and may be confused in the vegetative condition; both are densely cespitose. However, planispicata is distinguishable from its purplish shoot bases (versus whitish to light brown) and slightly broader leaves (up to 3.5-6.5 mm versus 2-5.3 mm).