Iris virginica, commonly called Southern blue flag, is a wetland species of iris. It typically grows to 2' tall (less frequently to 3') and features non-fragrant violet-blue flowers with falls that are crested with yellow and white. Flower color can vary considerably from very light blue to purple. Bright medium green, sword-shaped leaves often lie on the ground or in the water. Blooms in late spring.
Var. shrevei is native to inland swamps, marshes and flood plains in central North America (Ohio and Mississippi River basins and throughout the Great Lakes) including somewhat broad distribution in northern and central Missouri. Var. shrevei is similar in appearance to the species, but prefers a more neutral soil and is reportedly easier to grow in Illinois home landscapes.