Meet your Chicagoland Stormwater Storage Requirements with a rain garden!

Rain Garden Plant Profiles: Blue Flag Iris

Iris virginica shrevei (Blue Flag Iris)

Sun Requirements: Part to Full Sun
Soil Moisture: Medium to Wet
Average Height: 3′
Bloom Time: May-July
Bloom Color: Purple
Rain Garden Uses: Bottom and Sides of Basin
My Notes:

      A staple rain garden plant; widely adaptable, easily established, long-lived, and
     well-behaved spreading slowly by rhizomes.

      Prefers consistent moisture but tolerates both flooding and drought; the more sun it
     receives the more it will bloom.

      Flower is seen best up close as the foliage will often be taller and hide the flower
     from view.

      Appreciated for its spikey foliage which adds a fine texture to the garden and at 3′ tall
     this native to the Midwest does not overpower the space.

Native Range:

Kartesz, J.T., The Biota of North America Program (BONAP). 2013. Taxonomic Data Center. ( Chapel Hill, N.C. [maps generated from Kartesz, J.T. 2013. Floristic Synthesis of North America, Version 1.0. Biota of North America Program (BONAP). (in press)]

Site: Part Sun, Wet, Clay soil

1st Year

2nd Year

3rd Year

Partial Sun gets modest blooms as flowers are hidden in foliage.

Iris is one of the first plants in Spring to “green-up.”

Site: Part Sun, Medium Wet, Loam soil

1st Year

2nd Year

3rd Year; notice flopping due to drought.

4th Year; rebounded nicely from previous dry year.

Iris colonizes but does not take over.

Chelone glabra (White Turlehead) is a great companion plant to Blue Flag Iris as they prefer similar growing conditions. You can see the long blades of the Iris in the background of this photo. If this is done, I would recommend cutting back the White Turtlehead to 2′ in early to mid-June to increase its bloom and keep their heights similar.


Clumps of Iris dug up and set into large containers until ready to be divided.

The clump has been hand-divided into individual root stocks. This is done by teasing them apart from each other gently, and sometimes forcefully. I create a mix of roughly 2 parts sand, 1 part compost, and 3 parts top soil for their transplanting soil. This soil is heavy, but the materials are plentiful in my yard.

After filling the containers with the soil I take a handful and pull it aside for the root stock, then bury the root being sure to get all the fibrous little roots into the soil.

These twelve plus plants came from one large clump and each will be quite large by next season.

If you have used Blue Flag Iris in your garden let me know how it went for you below!

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