Are these blue flag irises? #643672 - Ask Extension


Are these blue flag irises? #643672

Asked May 31, 2020, 8:45 AM EDT

I have tried to use online sources to ID these irises, but I am still uncertain whether they are native blue flag irises. They are outgrowing this patch of garden and I would like to thin them out and plant some elsewhere in my garden if they are the native species. They were here when we bought our house 2 years ago and I have no idea how aggressively they spread and would love to know if I should be careful with them in other parts of my garden. Thank you!

Prince George's County Maryland

Expert Response


Thanks for your question. I believe the perennial in your photos is a Siberian iris (Iris siberica). I have them growing on the side of my home too. They are not aggressive but the clumps will eventually get thicker in the garden bed. I have had them growing in a 2 ft wide bed for 30 years and have only divided them at most twice.

It is alright to divide the clumps and plant them elsewhere or share them with a friend. I would wait until the blooming period is over before dividing them. I found that the number of blooms diminishes as the plants get more crowded in the space. It is a good practice to remove the developing seed pods after each bloom has fallen. That will send the plant's energy into producing more flowers instead of producing viable seeds. However, the dried seed pods can be an interesting addition to a flower arrangement. Siberian iris is not native.


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