This is widespread across eastern states but mapping here is provisional. Based on incomplete colls. villosa is easily confused with quaternata, which has been combined in some treatments (e.g. FNA 26 and recent W). It usually occurs on damper sites, often in riparian woods and swamps. D. villosa is best distinguished (Al-Shehbaz & Schubert 1989; Cr, W) by having a mostly twining stem with alternate leaves (except rarely, at the base with short internodes, appearing almost whorled). D. quaternata has lower leaves in whorls of 4-7, and only the upper stem twines with alternate leaves. Also, villosa has stems with 8-14 narrowly winged ribs (versus terete); its rhizomes are ca. 5-10 mm thick (versus 10-15 mm), relatively straight and little-branched (versus often contorted and branched); fruits tend to be smaller (F); 2n = ?20 or 60 versus 36 or 54 (Cr, FNA 26).