The best sites are concentrated in the St. Lawrence Glacial Lake Plain Subsection of the St. Lawrence and Champlain Valley Ecoregion in Jefferson County. Other examples are located in the Eastern Ontario Lake Plain, the St. Lawrence Glacial Marine Plain, and Champlain Glacial Lake and Marine Plain. Additional small sites occur along the Onondaga Escarpment and the Helderberg Highlands.

This community is mostly limited to the Great Lakes basin. This community has been described from Ontario, where this and related communities are called "alvar." The range is estimated to span north to southern Ontario, west to northern Michigan, south to the Helderburg Highlands of central New York and east to the Lake Champlain Valley of New York and Vermont.