Amer. J. Sci. Arts, ser. 2, 9: 29. 1850.
Plants loosely cespitose or not, long-rhizomatous. Culms solitary or not, erect, 50–130 cm. Leaves 4–7; basal sheaths brownish; sheath of distal leaf 3–21 cm; ligules rounded to triangular, 6–28 mm; blades 30–80 cm × 6–13 mm. Inflorescences 6–40 cm; peduncles of proximal spikes 1–13 cm, basal 2 peduncles 2–17 cm apart; of terminal spikes 1–12 cm, shorter than to somewhat exceeding the distal pistillate spike; bracts leafy, sheath 1–9 cm; blades 20–70 cm × 4–11 mm. Spikes: proximal pistillate spikes 2–6, the distal usually ± crowded, ascending, densely 8–90-flowered, usually cylindric, 2–8 × 1.5–3 cm; terminal staminate spikes 1–2, 2–10 cm × 2–5 mm. Pistillate scales 3–9 veined, lanceolate, 6–13 × 1.8–3.2 mm, apex acute to awned, awn rough, to 5.5 mm. Anthers 3, 3.5–7 mm. Perigynia ascending to spreading, strongly 17–25-veined, sessile, lanceovoid, 12–18.5 × 3.8–6 mm, shiny, glabrous; beak conic, 6–9 mm. Achenes stipitate, rhombic, concave faces, angles thickened, prominently knobbed with hard, nipplelike points, 3–4.5 × (2.2–) 2.4–3.4 mm; style same texture as achene.
Phenology: Fruiting late spring–summer.
Habitat: Wet forests, especially in openings around forest ponds, riverine wetlands, marshes, wet thickets
Elevation: 0–500 m
Ont., Que., Ark., Conn., Del., Fla., Ga., Ill., Ind., Iowa, La., Md., Mass., Mich., Miss., Mo., N.J., N.Y., N.C., Ohio, Okla., Pa., S.C., Tex., Vt., Va., W.Va., Wis.
Carex lupuliformis is rare and local throughout much of its range, especially northward.