Although ranging widely across eastern North America, this biennial occurs mostly in somewhat base-rich wetlands of northern regions. Variation deserves further attention; 2n = 20-23 and 30 (FNA 19, Y). In Ky. and some other Appalachian states (Tenn., N.C., Va., W.Va. and perhaps further northeast based on colls. at GH), muticum usually occurs on relatively mesic sites with medium acid soils, especially along roads and trails on lower slopes in the Rugged Hills of the Appalachian Plateaus. In these hills, it is often more robust, with relatively large heads and less deeply pinnatifid leaves. These plants with less deeply pinnatifid leaves have been treated as var. subpinnatifidum (Britt.) Fern. (or a forma in F). However, variation may be too continuous across the whole range of muticum for segregates to be readily recognized. (A somewhat parallel ecological distinction may exist within Eutrochium maculatum.)