Blueflag’s sword-like leaves emerge from thick horizontal root stock (corm) which are covered with fibrous roots. This emergent will grow to heights of four feet in spreading clumps. The individual leaves are somewhat shorter than the entire plant. This species will radially grow less than 2 feet per year.

From the nearly straight flowering stems emerge large blue to violet-blue showy flowers. They bloom from May to July. The three petaled flowers are often finely variegated with yellow, green, and white. The flower develops a three celled capsule which is about 1 1/2 inches long and 3/4 of an inch in diameter. Within each cell, two rows of flattened round seeds form. There are an average of 18,000 seeds per pound.