This occurs mostly on the Gulf Coastal Plain and upstream into the central Mississippi Valley; the closely related species, J. ovata (Walter) Lindau, is restricted to the Coastal Plain from Ala. to Va. (W). Both species usually occur along shorelines of sluggish or stagnant waters. J. lanceolata differs in its lax spikes with single secund flowers (versus congested with opposite pairs of flowers), its smooth seeds (versus minutely muricate), and its more elongated leaves (L/W = ca. 5 versus 3).