Sweet flag is a perennial, rhizomatous, iris-like herb. The erect, sharp-pointed, sword-shaped leaves fan-out from a pinkish base and grow to 5 feet in length. The midvein is usually off-center. Cut or bruised leaves produce a sweet, tangerine-like scent. The flower stem, or scape, arises from the base of the outer leaves. Although resembling a leaf, the scape is triangular in cross section. A long, erect bract, or spathe, extends beyond the scape. A single, cylindrical 2 to 4-inch spike, or spadex, angles upward at this union. The slightly curved spadix is crowded with small yellowish-green to brown flowers that appear from May to July. Sweet flag has thick, creeping rhizomes with brownish exteriors and white, fleshy interiors.