Mapping here is tentative. This species has often been treated as a variety (K) or subspecies (FNA) of ramosissimum, which may intergrade (Cr). Ranges are widespread across North America and similar, but both taxa are relatively uncommon to rare in southeastern states (W), P. prolificum appears more concentrated on saline soils. FNA 5 reported prolificum from Ky. M reported colls. from roadsides in BALL and MERC; and there may be a coll. from BALL at FI. Possible colls. from OLDH (DHL) and TRIM (MM) are immature or otherwise uncertain. A large population (with 1000+ plants) has recently been found near the old Mann's Lick of southern JEFF (JC for APSC; see also www.inaturalist.org/observations/312318706). See also notes under Polygonella americana.