In its broad sense, including praemorsa, this species is widespread across eastern and central North America (Cantino 1982). But in its strict sense, as mapped here, virginiana is mostly northeastern (K) and generally associated with riparian shorelines and similar sites. P. purpurea (Walt.) Blake (= P. denticulatum (Ait.) Britt.) is a closely related species that occurs on the Coastal Plain from N.Car. to La. (Cr, W; colls. at NCU). In Ky. virginiana is distinct from praemorsa and restricted to low rocky banks and marshy cobble bars along larger free-flowing streams and rivers, with limestone or sandstone as bedrock. It has almost disappeared from the Ohio River banks and from the Kentucky River watershed, presumably due to impoundments; Short collected it ca. 1840 from "islands at the falls of Ohio" in JEFF, and at "borders of Ky. River [at] mouth of Hickman Creek in JESS (PH). However, MM did collect it on "flat limestone shoals by Sand Island" at the Falls of Ohio in 1981 (APSC); and H. Bryan collected it on banks of the Kentucky Rv. at mouth of Stony Cr. in 1981 (EKY). P. virginiana is a relatively short plant, with smaller leaves and running rhizomes; see notes under praemorsa. Its relatively small, pale flowers appear in Jun-Aug, at the same time as commonly associated Justicia americana.