Iris versicolor

Common Names

Blue Flag, Harlequin Blue Flag, Northern Blue Flag, Larger Blue Flag, Blue Flag Iris, Purple Iris, Large Blue Iris, Liver Lily, Snake Lily, Wild Iris, Boston Iris, Particoloured Iris, North American Blue Flag

Summary

Blue Flag, a rhizomatous perennial in the Iridaceae, is native to marshes, swamps, wet meadows, ditches, and shorelines of eastern North America. It forms dense clumps with sword-like leaves and bears tall stems of violet-blue to blue-purple flowers, often with a yellow basal patch and veining; blooms occur in late spring to early summer, and overall height ranges roughly 2–3 ft, with spreading via creeping rhizomes to form colonies.

Preferred conditions include full sun to partial shade in consistently moist to wet soils, such as along ponds, water gardens, rain gardens, or moist borders; shallow standing water or brief submergence is tolerated. Propagation occurs by division after flowering or by seeds; maintenance is minimal. It is deer-tolerant and attractive to pollinators; rhizomes are poisonous if ingested and may irritate skin, so gloves are recommended when dividing.

Lifecycle

Perennial

Height

8 inches-5 feet

Spread

2-3 feet

Hardiness Zones

Zones 3-9

Sunlight Requirements

Ideally full sun; range from full sun to partial shade.

Soil Type

Moist to wet, rich loamy soil that is humus-rich and acidic, tolerating standing water up to 4 inches

Soil Drainage

Consistently moist to wet soils; tolerates shallow standing water (2–4 inches).

Soil pH

6.5-7.0

Bloom Color

Blue to purple

Bloom Time

Spring and Summer

Foliage Color

Blue-green

Fall Foliage Color

Green

Leaf Lifecycle

Deciduous

Growth Rate

0-2 feet per year, slow-spreading

Seasons of Interest

Spring and Summer

Propagation Methods

Seeds, Cuttings, Division

Attracts Wildlife

Attracts hummingbirds and insect pollinators (bees, butterflies, moths, beetles)