This largely mid-western species is centered in the central to upper Mississippi watershed. It typically occurs on rocky streambanks and terraces, less often on uplands. Several variants have been described from other states, with both diploids and triploids, but these need further assessment (D, F, Gl, St, M, Lance 2006, FNA 9). Also, hybrids are possible with collina, crus-gallii, uniflora or related species; the cross with uniflora (X vailiiae Britton) has been reported from e. Ky. (W). Section Macracantha (including succulenta) is distinguished from section Coccineae (including Parviflorae to Pruinoseae) by its seeds deeply pitted or eroded (versus plane to concave); fruits orange to red (versus usually red to purple or black but often remaining green until late); inflorescences with mostly 10-20 flowers (versus 1-10) in compound corymbs (versus cymes or coyrmbs); flowering usually in late May to early Jun (versus late Apr to mid May); floreal leaves (2) 3-5 (8) cm wide, unlobed or shallow-lobed, cuneate (versus 1-8 cm wide, usually lobed and abruptly narrowed to subcordate).