Ptilimnium costatum (Elliott) Rafinesque. Phen: Jun-Oct; mid Jul-Oct. Hab: Tidal freshwater marshes, wet prairies, bottomland hardwood forests. Dist: Se. NC south to GA, and west to IL, MO, and AR (material from LA and TX is of P. texense); it is rare and disjunct through much of that range. Reported for Georgetown County, SC (Bradley et al. [in prep.]).
Origin/Endemic status: Endemic
Other Comments: It has the potential to be a great deal larger and coarser than any other member of the genus, but individuals will be encountered no larger than a fairly robust plant of P. ahlesii or P. capillaceum.
Synonymy: = Ar, C, F, G, GW2, Il, K1, MC, Mo2, Ok, RAB, S, Tn, Easterly (1957), Feist (2010), Feist et al (2012), Weakley & Nesom (2004); < Ptilimnium costatum (Elliott) Raf. – K3, K4