Panicum virgatum aka Blackwell Switchgrass

Panicum virgatum, or switchgrass, is a perennial in the grass family. This warm-season grass forms part of the North American tallgrass prairie. Its native range spans southern Canada, much of the United States, and Mexico. It also reaches Honduras and Cuba. It grows in prairies, open woods, and along streams. Wild plants occupy both wet and dry ground.

Garden clumps reach about 3–6 feet [0.9–1.8 metres] tall. Flower stems can reach 7 feet [2.1 metres]. Clumps spread to about 3 feet [0.9 metres] wide. RHS gives a lower height range of 1.6–3.3 feet [0.5–1 metre]. Botanical records include stems reaching nearly 10 feet [3 metres]. Short, creeping rhizomes let the dense clumps spread slowly. The round, stiff stems support narrow green leaves with a blue cast. Each leaf has a clear midrib and hairs near its base. Leaves turn yellow or orange in fall, then tan for winter.

Loose, branched panicles rise above the leaves in summer and fall. The small flowers show pink, purple, or brown tones. Wind carries the pollen. Bloom dates vary by source and growing site. Chicago lists July and August; NC State gives June through October. The small, teardrop-shaped grains turn from pink or purple to tan. Seed heads add winter form and feed birds and small mammals. The clumps give wildlife cover through the year. Several skipper butterflies and the common wood-nymph use it as a larval host.

Full sun helps the stems hold their upright shape. Partial shade can make clumps loose and prone to falling. Rich soil can also cause stems to flop. Switchgrass prefers moist ground but tolerates drought and brief flooding. It grows in sand, clay, loam, or chalk. It accepts acid, neutral, and alkaline soils. Sources list USDA zones 5–9 and RHS hardiness H5. Cut old stems and leaves down in late winter or early spring. Raise new plants from seed or divide clumps in spring.

Use switchgrass in borders, screens, meadows, and rain gardens. It also suits pond edges and helps hold soil against erosion. Stems serve as fresh or dried cut material. Researchers also study it as a biofuel crop. Deer seldom browse it, but dry growth poses a high fire risk. It can self-seed and become weedy outside its native range. Thrips, mites, and Japanese beetles sometimes attack it. Rust and crown or root rot can also occur. Edibility sources conflict: NC State lists edible seeds, while PFAF reports no known food use. PFAF reports toxicity in horses, sheep, and goats despite its general hazard entry.