This species prefers neutral or slightly acid soils and is found mostly in marshes and swamps in the lake area although it was found also in the Bacon Bog in Marion County. It is variable in the pubescence of the leaflets. In the middle of September I studied this species on the south shore of Long Lake in Porter County where the shore is over a hundred feet wide. I was able to study the plants from near the water line back to where it was too dry for the species to grow. I found that the leaves varied in pubescence from nearly glabrous in the wettest situations to silky-pubescent in the driest places.
Stems coarse, somewhat woody below, reddish- brown, 2-6 dm, decumbent or ascending from a long rhizome, rooting below; lvs long-petioled, pinnately compound; lfls 5-7 (the upper 3 adjacent), narrowly oblong to elliptic, 5-10 נ1-3 cm, sharply toothed, glaucous beneath; infl leafy, few-fld; fls red-purple, 2 cm wide; bractlets narrowly lanceolate, much shorter than the acuminate sep; pet half as long as the sep; style lateral; achenes smooth, attached to the enlarged, spongy receptacle; 2n=28, 35, 42, 62-64. Swamps, bogs, and streambanks; circumboreal, s. to N.J., O., Io., and Calif. June-Aug. (Comarum p.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.