This showy plant is a gorgeous addition to a shoreline, rain garden or even a wet perennial bed.  I love it both for the bright color of the flower and the graceful leaves that add an appealing vertical accent to the landscape.  The rhizomatous root has been used medicinally by many cultures, although it is considered to be toxic.

The Facts:

Zones: 3-9
Native to: all of Minnesota
Height: 2 to 3 feet
Spread: can spread up to 2 feet a year
Flower:  a blue or purple flower 2-4” wide, growing 2 to 3 per stalk.  The true petals are located in the center and are surrounded by 3 larger sepals, which are showy and are marked with yellow and white.
Bloom:  May to July
Leaves:  basal, sword-shaped, about 1” wide and 8 to 32” long
Sun:  full sun or light shade

Garden Tips and Uses:

This plant is found growing naturally along lakeshores, wet prairies and in shallow bogs and marshes, so obviously it requires wet garden conditions.  It can be grown in a water garden, a rain garden, or even planted in a poorly drained perennial bed.  Earth Wizards has used the Northern Blue Flag in a number of rain gardens and it adds a nice contrast in both color and shape.  This plant propagates both by seed and rhizome, and given the right conditions, can fill in an area nicely.  We’ve had great success using it in our shoreline restoration projects where it forms attractive clumps, and it is not such an aggressive spreader that it overtakes other plants.  The Northern Blue Flag Iris can be divided every three years to maximize blooming.

Caution:

There is a non-native aquatic iris that has escaped cultivation and is overtaking the natural habitat of the Northern Blue Flag.  This aggressive, invasive iris is yellow, has leaves that are less than 1” wide and is called the Pale Yellow Iris (Iris pseudacorus).  Please do not plant this species!