Carex pensylvanica aka Pennsylvania Sedge

Carex pensylvanica is a perennial in the sedge family, Cyperaceae. Its common names include Pennsylvania sedge and oak sedge. It grows in central and eastern North America. Its range stretches from Quebec and Manitoba south to Georgia and Mississippi. It lives in thickets, dry woods, and shaded rock ledges. It often grows near oaks. NC State notes uncertainty about the identity of some southern populations.

This low plant forms loose clumps and spreads through rhizomes. Growth is slow, but colonies can cover the soil. Garden plants reach about 0.7–1 foot (0.2–0.3 m) tall. A clump spreads about 1 foot (0.3 m) wide. The roots have a red-brown tint. Soft, narrow green leaves arch from the base. Each leaf can exceed 0.5 feet (0.15 m) in length. The blades have smooth edges and no hairs. Leaves may turn yellow in fall. Some foliage stays green through winter, but severe cold kills it back.

Small flowers appear in spring, from April through June across sources. Missouri Botanical Garden lists May as the bloom month. Rough stems with three sides hold the flower spikes. Each plant bears both male and female flowers. The male flowers sit above the female flowers. Their scales show green, purple, brown, and white tones. The blooms add little show compared with the leaves. Small, dry fruits called achenes appear in May and June. Birds and small mammals eat them and shelter among the plants. The leaves also support caterpillars of some satyrine butterflies.

This sedge grows best in partial to full shade. It prefers loose, well-drained loam with dry to moderate moisture. It also grows in sandy soil rich in organic matter. Acid to neutral soil suits it. It tolerates deep shade and periods of wet soil. NC State advises against full sun and notes better performance in cooler climates. Sources place it in USDA zones 3–8. Care needs are low. Gardeners can divide clumps, while seed can prove hard to establish. Plants may also seed themselves where conditions suit them.

Use it beneath taller perennials or as woodland ground cover. It can replace lawn in shade but cannot bear heavy foot traffic. Leave it unmown, or mow a few times each year. It also helps hold soil in place. Serious pest and disease trouble is uncommon. Leaf spot, rust, smut, and anthracnose can occur. Aphids and fungus gnat larvae may also cause problems. Plants For A Future lists no known food or medicinal uses. That source reports no known hazards, rather than confirmed safety.