Iris prismatica Pursh

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.

Chile Central

Iris prismatica, the slender blue flag or cubeseed iris, is a plant species native to parts of the southern and eastern United States from Maine south to Alabama, as well as to the Canadian provinces of Ontario and Nova Scotia.

Iris prismatica is a perennial herb spreading by means of rhizomes that are close to the surface of the soil. Flowering stalks can reach a height of 80 cm. Leaves are long and narrow, up to 60 cm long but rarely more than 5 mm across. It has 2–3 blooms in May. Flowers are pale blue to blue-violet. It tends to grow in swampy, wet conditions, and within the United States, it is currently state listed as 'threatened' in Maine, New Hampshire, New York, and Tennessee, and state listed as 'endangered' in Maryland and Pennsylvania. It is cold hardy to USDA Zone 3.

Iris prismatica là một loài thực vật có hoa trong họ Diên vĩ. Loài này được Pursh miêu tả khoa học đầu tiên năm 1814.