This species has a remarkable range in North America, with five largely disjunct centers: (1) lowlands of New England; (2) lowlands south of Lakes Erie and Ontario; (3) the Allegheny Mts.; (4) a zone from the Shawnee Hills to the southern Cumberland Plateau; and (5) the Ozark Mts. (FNA 24, K). Closely related plants (known as ssp. japonica) occur in East Asia (Koyama & Kowano 1964). Typical acutiflora occurs in similar habitats to septentrionalis, but generally on more acid soils in boggy non-alluvial ponds that tend to dry up in summer. 2n = 40.