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Illinois Native Plant Guide - Blue Flag Iris - Pages 94-95

Illinois Native Plant Guide

Blue Flag Iris (Virginia Blue Flag) (Wild Flag)
Iris virginica (Iris virginica shrevei)

Preferred Water Depth and Inundation Tolerance

Prefers wet meadow zone, seasonally flooded to a depth of 3 inches early in the spring. Species will not tolerate constant inundation of more than 6-8 inches.

Wildlife Value

Seeds are eaten by waterfowl and muskrat. Hummingbirds have been observed feeding on nectar. Also provides cover for amphibians, foraging habitat for snakes, and habitat for many insect species.


Used in lower shoreline zones and vegetated swales.

Availability, Establishment, and Maintenance

  • Seeds, transplants, and rhizomes are available from several commercial vendors.
  • Seeds require cold, moist stratification for 120 days. Alternatively, they can be planted on the soil surface in the fall. Warm spring temperatures (higher than 75o F) and light will trigger germination.
  • Locally, few positive results have been observed from seeding on-site. Seeds are usually eaten by birds and insects.
  • In the greenhouse, 99% germination has been observed from seed in 9 days.
  • Rhizomes and transplants should be planted in the spring.
  • Rhizomes may be temporarily refrigerated until planting. Plant them in 2-3 inches of soil on 0.5-1.5 foot centers, allowing growing points to be visible above the soil surface.
  • Young shoots should not be inundated by water.
  • CAUTION: Severe dermatitis may result from handling rhizomes.

Blue Flag Iris (Virginia Blue Flag) (Wild Flag)
Iris virginica (Iris virginica shrevei)

Mature Height
Up to 2.5 feetBlue Flag Iris (Virginia Blue Flag) (Wild Flag)

Plant Type
Perennial emergent herb

Indicator Status

Not available

Nutrient Load Tolerance

Salt Tolerance
Not tolerant

Siltation Tolerance

Flowering Color and Time
May to July

Light Preference
Partial to full sun

Seeding Rate
.06 - .25 lbs/acre

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