Color, violet blue, streaked with yellow. The slender blue flag resembles the larger species in its flower and leaves. (See Larger Blue Flag, p. 300.) The whole plant is more delicate. Flowers, on slender, long pedicels, appear singly or in pairs. The outer, recurved perianth segments are about 2 inches in length. The 2 or 3 leaves are linear, like blades of grass. Stem, round, 1 to 3 feet tall. Rootstock slender. June and July.
Colors, dark purple, crimson, and white. (See Purple Flowers, p. 302.)