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 similar, but prolificum appears more concentrated on saline soils. FNA 5 reported prolificum from Ky. M reported colls. from roadsides in BALL and MERC; and there appears to be a coll. from BALL at FI. Reports from OLDH and TRIM may be based on typical ramosissimum. See also notes under Polygonella americana.