In Ohio, the rare hemlock hardwood swamp community only occurs in Ashtabula County, mostly on the Lake Erie coastal plain or in the Grand River lowlands. Now 55 acres of this unique habitat is protected as Conneaut Swamp State Nature Preserve. The preserve is part of the 86-acre Conneaut State Wildlife Area.

The hemlock swamp contains a diverse mix of trees including hemlock, yellow birch, beech, tulip poplar, sycamore, cucumber magnolia and a variety of oaks and maples. Beneath the canopy lies a mix of sedges, grasses and wildflowers.