Monographs Details: Triosteum perfoliatum L.
Authority: Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Description:Species Description - Coarse herb to 13 dm; stems crisp-hairy, the abundant hairs mostly less than 0.5 mm; lvs obovate, ovate-oblong, or subrhombic, the main ones 10–30 × 4–15 cm, narrowed below the middle but broadly connate-perfoliate at base (3–9 cm wide where united), sparsely setose above, usually densely and softly hairy beneath; fls (1–)3–4 per axil; sep 10–18 mm, ca 1.5 mm wide, finely and uniformly hairy on the back and margin, often also glandular; cor 8–17 mm, crisp-hairy, purplish to dull greenish-yellow, the style exsert ca 2 mm; frs subglobose, dull orange-yellow; 2n=18. Woods and thickets, often in thin or rocky soils; Mass. to s. Ont. and Minn., s. to S.C. and Okla. May–July.
Common Names:perfoliate horse-gentian