Wet areas: swamps, stream margins, swamps, seepy shores and banks, cedar swamps, rocky to sandy shores, often in somewhat disturbed areas, such as ditches or trails in moist forests, rarely in dry ground.

Although the stems are often described as pubescent, at least on plants not growing in water, the great majority of our specimens have glabrous stems. Small plants in drier places are not always easily distinguished from C. parviflora. A very few specimens of C. pensylvanica have been seen with sparsely ciliate petioles on the cauline leaves, especially from the western Upper Peninsula, but the plants are so tall and the leaf segments so broad that they can be readily separated from C. flexuosa or C. hirsuta, besides being in mostly natural settings.