This is the only iris native to Wyoming. It is common in moist areas across the state. Its name refers to the Missouri river, not the state; it was first collected by Lewis and Clark on their expedition in 1806. Leaves are silvery-blue, slender, and strap-like. Each flower stalk usually produces several pale blue to purple flowers with yellow highlights on the petals. Though generally considered a wetland plant, it can tolerate very dry conditions and will bloom so long as the soil remains moist in the spring and early summer. They are sometimes considered a weed in hay fields.
Width: expands slowly to form large clumps
Water needs: moderate to high in spring
Exposure: full sun
Availability in nurseries: common
Native range: western North America (WY native)
Plant family: Iridaceae