Although it’s commonly found in wet ditches and swamps, this graceful, sword-leaved, 3-foot beauty survives with minimal care in home gardens. It thrives in full or partial sun and moist, loamy soils, but it adapts to other types of soils as long as they aren’t overly dry. In Greek mythology, Iris was the goddess of the rainbow, and blue flag’s down-curved petals and sepals are an eye-catching combo of blue violet and yellow.
A colony of irises will brighten the landscape for a month, using its highly specialized flowers to attract the attention of pollinators. Because they have to compete with many other blooming flowers, they have developed large and colorful blossoms with upright petals (the flag) that catch the attention of insects. The sepals are shaped into a sort of landing pad, even equipped with a yellow “runway” (the signal) that guides the visitors into a narrow passage leading to the nectar glands. Along the way, they brush by the pollen-producing anthers, picking up pollen that they carry to the next flower they visit. Even hummingbirds are drawn to the inviting blossoms.
Eastern North America has two common native irises: iris versicolor (pictured first), aka northern flag and Harlequin flag, and Iris virginica, aka southern flag. Northern blue flag is more cold hardy than its southern counterpart. Both are much preferred to iris pseudoacorus, or yellow flag iris, which is an extremely invasive plant that easily outcompetes our natives. In addition, its plant parts are toxic and unappealing to our wildlife.
Versicolor and virginica share many similar traits and are often sold interchangeably as “blue flag iris.” To differentiate between the two, remember that virginica has a bright yellow signal and leaves that extend above the flowers, whereas versicolor has a greenish-yellow signal, prominent dark-purple veins, and leaves that don’t extend above the flowers.
Native habitats include meadows, wet ditches, stream banks, marshes, and swamps. It thrives in wet areas, rain gardens, and along the edges of water features. While it tolerates standing in up to six inches of water, it can be potted and sunk into the water. Though it can tolerate dry spells, it appreciates water and a light layer of mulch to help retain moisture.
Grows in full and part sun.
Grows 2-3’ tall and 1-2' wide.
Prefers moist, rich, loamy soil, but will grow in other soils with enough moisture.
Violet-blue flowers with purple veining and a central yellow patch sit atop unbranched stalks, blooming between May and July. Each flower spans up to four inches and is later replaced by a capsule jammed with seeds that spread via water.
The plants also spread by rhizomes to form colonies.
Sword-shaped bluish-green or green leaves with smooth margins are up to 3’ tall and mostly erect.
Blue flag irises are a host plant for 13 species of Lepidoptera larvae, including the beautiful Virginia ctenucha moth. Hummingbirds also find these flowers attractive.
Medicinal, Edible, and Other Uses:
The poisonous rhizome was used by colonists, with guidance from Native Americans, for various healing purposes. The roots have been used for medicines that treat skin infections, syphillis, dropsy, and stomach problems. Today, it is used to purge the liver.
Some tribes used the two outermost fibers of the leaves to spin strong, very fine twine. Powdered iris root, called orris, smells like violets and has been added to perfume and potpourri.
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