34. Iris prismatica Pursh, Fl. Amer. Sept. 1: 30. 1814.
Slender blue iris
Rhizomes superficial or only slightly buried in peaty soil, cordlike portions usually 1-branched, 40 cm × 2–5 mm, bearing scalelike leaves at nodes; nodal roots absent. Stems simple or 1–2-branched, 3–8 dm. Leaves: basal with blade slightly ribbed, 3–6 dm × 0.2–0.5 cm; cauline 1–4, erect. Inflorescence units 1–3-flowered, branch units 1–2-flowered; spathes pale brown, narrowly lanceolate, 2–4 cm, scarious or partially membranaceous. Flowers: perianth pale blue or blue-violet; floral tube 0.2–0.3 cm; sepals pale violet, veined deep violet basally, ovate, 4–5 × 1.3–2 cm, base abruptly attenuate; petals lavender, oblanceolate, 3.5–4.5 × 0.7–1.5 cm; ovary trigonal, sharply angled; style arched, narrow, 2–3 cm, crests divergent, quadrate, 0.5–0.7 cm, margins serrate; stigmas sharply triangular; pedicel somewhat flattened, 3–7 cm, exserted from spathe. Capsules sharply 3-angled, almost winged, 3–4 × 1.2–1.4 cm, concave faces 6–14 mm wide. Seeds in 1 row per locule, buff to dark brown, pyriform, with convex sides, 3–4 mm, smooth. 2n = 42.
Flowering Apr--Jul. Swampy, peaty soil; Ala., Conn., Del., Ga., Ky., Maine, Md., Mass., N.H., N.J., N.Y., N.C., R.I., S.C., Tenn., Va.