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collage of Northern Blue Flag and Southern Blue Flag

Northern Blue Flag (Iris versicolor) vs. Southern Blue Flag (Iris virginica)

Updated June 26th, 2024

These two species are visually similar, but there are numerous small differences that can be used to distinguish them, particularly when they are in bloom. They have a narrow band of overlap through VA, MD, WV, OH, MI, and MN, but both can be planted in gardens outside their native ranges. These species are closely related and can hybridize in the wild, horticultural hybrids are widely planted, and hybrids are fertile thus leading to backcrosses and intergrades, so it may not be possible to identify all plants to species level. These species mostly inhabit similar habitats. I. versicolor may tolerate slightly more shade, whereas I. virginica may be slightly more likely to occur in disturbed habitats like roadside ditches.

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