27. Iris virginica Linnaeus, Sp. Pl. 1: 39. 1753.
Southern blue flag, iris de Virginie
Iris caroliniana S. Watson; I. georgiana Britton; I. shrevei Small; I. virginica var. shrevei (Small) E. S. Anderson
Rhizomes many-branched, forming dense clumps, 2–4 cm diam., usually covered with remnants of old leaves; roots fleshy. Stems rather weak, often falling over after flowering, solid, usually 1-branched, 5–10 dm. Leaves: basal erect or often flexible, blade gray-green to bright green, buff to purplish basally, with several prominent ribs in mature leaves, linear-ensiform, 6–8 dm × 2.5–3 cm, apex acute. Inflorescence units 2–3-flowered, branch units 1–2-flowered; spathes compact, often with brown striations, ridged, unequal, outer 3–8 cm, inner 8–14 cm, firm, herbaceous. Flowers: perianth lavender to violet, rarely white; floral tube constricted above ovary, 1–2 cm; sepals spreading and arched, pale blue to purple with darker blue or purple lines, obovate to oval, 4–8.4 × 1.6–4 cm, base abruptly attenuate, claw green in median, bordered by yellow ground with blue or purple lines, yellow extending onto base of limb as finely pubescent signal patch; petals oblong-lanceolate to oblong-spatulate, 3–7 × 1–3 cm, claw greenish yellow with blue or purplish lines, apex often emarginate; ovary trigonal, 1.3–3.8 cm; style inwardly auriculate at convergences, 3–4.5 cm, crests reflexed, 0.7–2 cm; stigmas unlobed, with prominent triangular tongues, margins entire; pedicel 2.5–8 cm. Capsules ovoid, ellipsoid, or long-cylindric, trigonal or polygonal in cross section, 3–6 × 1–2 cm. Seeds in 2 rows per locule, pale brown, usually D-shaped, 5–8 mm, pitted, corky. 2n = 70, 72.
Flowering May--Jun. Wetlands, margins of lakes and streams; Ont., Que.; Ala., Ark., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Md., Mich., Minn., Miss., Mo., Nebr., N.Y., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Va., W.Va., Wis.
Plants of Iris virginica from the southeastern and south-central states having stems 2–3-branched and seldom falling to the ground after flowering, and with capsules long-cylindric have been recognized as var. shrevei.