Schweinitz's Flatsedge occupies sites with exposed, sandy soil, including Atlantic and Great Lakes dunes, as well as disturbed sites at pine barrens and oak openings in the interior of the state. It may persist in the seed bank for many years and rapidly colonize a site when disturbance creates good habitat. (New York Natural Heritage Program 2008). Sandy soil (Gleason and Cronquist 1991). Riverbanks, sand bars, lakeshores, sand dunes, sandy openings in woods; 1-1000m (FNA 2002). Sandy shores, dunes, dry prairies, fields, and roadsides (Voss 1972).

Great Lakes dunes A community dominated by grasses and shrubs that occurs on active and stabilized sand dunes along the shores of the Great Lakes. Unstable dunes are sparsely vegetated, whereas the vegetation of stable dunes is more dense, and can eventually become forested. Maritime dunes A community dominated by grasses and low shrubs that occurs on active and stabilized dunes along the Atlantic coast. The composition and structure of the vegetation is variable depending on stability of the dunes, amounts of sand deposition and erosion, and distance from the ocean. Maritime pitch pine dune woodland* A maritime woodland that occurs on stabilized parabolic dunes. The substrate is wind and wave deposited sand that is usually excessively well-drained and nutrient poor. The community is subject to high winds, sand-blasting, salt spray, and shifting substrate. * probable association but not confirmed Oak openings A grass-savanna community that occurs on well-drained soils. In New York, these savannas originally occurred as openings within extensive oak-hickory forests. The best remnants occur on dolomite knobs.

Pitch pine-heath barrens* A shrub-savanna community that occurs on well-drained, sandy or rocky soils. The most abundant tree is pitch pine and the shrublayer is dominated by heath shrubs. * probable association but not confirmed Pitch pine-oak-heath woodland* A pine barrens community that occurs on well-drained, infertile, sandy soils. The structure of this community is intermediate between a shrub-savanna and a woodland. Pitch pine and white oak are the most abundant trees. * probable association but not confirmed Pitch pine-scrub oak barrens A shrub-savanna community that occurs on well-drained, sandy soils that have developed on sand dunes, glacial till, and outwash plains.

Butterfly Milkweed (Asclepias tuberosa) Spotted Knapweed (Centaurea stoebe) (Cyperus filiculmis) Poverty Oatgrass (Danthonia spicata) Mountain Hairgrass (Digitaria cognata) Round-head Bush-clover (Lespedeza capitata)

Sundial Lupine (Lupinus perennis) White Sweetclover (Melilotus albus) Bouncing-bet (Saponaria officinalis) Little Bluestem (Schizachyrium scoparium) Maiden's Tears (Silene vulgaris)