Differentiating Iris Flowers: Learn About Flag Irises vs. Siberian Irises

By Mary H. Dyer, Master Naturalist and Master Gardener

There are many different types of iris, and differentiating iris flowers can be confusing. Some types are known by a variety of different names, and the iris world includes a number of hybrids too, which complicates things even further. Many people wonder how to tell the difference between flag iris and Siberian iris, two common types of iris plants. Read on to learn more about differentiating these flowers.

Flag Irises vs. Siberian Irises

So what is the difference between flag iris and Siberian iris?

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Flag iris plants

When people talk about “flag iris,” they are generally referring to wild iris. Flag iris includes blue flag (I. versicolor), commonly found in boggy areas and swamps of the northeastern United States, and yellow flag (I. pseudacorus), which is native to Europe but now found in temperate climates around the world. Both are types of beardless iris.

Blue flag iris is ideal for wildflower gardens where the plant has access to plenty of moisture in spring. It makes a good pond or water garden plant, as it performs well in standing water. This plant, which reaches heights of 18 to 48 inches, displays long, narrow leaves, sometimes gracefully curved. The blooms are typically violet blue, but other colors also exist, including intense violet and white with bright pink veins.

Yellow flag iris is a tall iris with stems that reach heights of 4 to 7 feet and upright foliage of about 5 feet, depending on growing conditions. The ivory or pale to bright yellow blooms may be single or double, and some forms may display variegated foliage. Although yellow flag iris is a lovely bog plant, it should be planted carefully, as the plant tends to be invasive. The seeds, which float, spread readily in running water and the plant may clog waterways and choke out native plants in riparian areas. The plant has done considerable damage to wetlands in the Pacific Northwest and is considered a highly noxious weed.

Siberian iris plants

Siberian iris is a hardy, long-lived type of beardless iris consisting of clumps of narrow, sword-like leaves and slender stems that reach heights up to 4 feet. The graceful, grass-like leaves remain attractive long after the flowers have faded.

Siberian iris types available in most garden centers are hybrids of I. orientalis and I. siberica, native to Asia and Europe. Although the plants grow well in wildflower gardens and along pond edges, they aren’t bog plants and they don’t grow in water. This is one sure way of differentiating between these and flag iris plants.

Siberian iris blooms may be blue, lavender, yellow or white.

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