4a. var. ambigua (Nutt.) Alph. Wood

P. verticillata var. dolichoptera Fernald

P. ambigua Nutt.

Stems unbranched or few-branched toward the tip. Leaves of the lower 1–3 nodes in whorls of 3–7, those of most nodes alternate. Inflorescences with relatively widely spaced flowers, at least toward the axis base. Wing sepals as long as or longer than the fruits. May–October.

Scattered in the Ozark and Ozark Border Divisions north locally to Pike County (eastern U.S. west to Wisconsin and Texas; Canada). Glades, upland prairies, openings of dry upland forests, and occasionally banks of streams and spring branches.