Content Detail

  • Family (English) Iris
  • Family (botanic) iridaceae
  • Tree or plant type Perennial
  • Native locale Illinois, North America
  • Size range Medium plant (12-24 inches), Large plant (more than 24 inches)
  • Light exposure Full sun (6 hrs direct light daily), Partial sun / shade (4-6 hrs light daily)
  • Hardiness zones Zone 3, Zone 4, Zone 5 (Northern Illinois), Zone 6 (City of Chicago), Zone 7, Zone 8, Zone 9
  • Soil preference Moist, Wet soil
  • Tolerances clay soil, Occasional flooding, Wet sites
  • Season of interest late spring, early summer, late summer, early fall
  • Flower color and fragrance Purple
  • Shape or form Arching, Open
  • Growth rate Moderate
  • Wildlife Butterflies, Hummingbirds, Insect pollinators
  • More information

    This native species of iris produces showy, purple flowers amid long, grassy leaves from late spring to early summer. This species grows in moist to wet soils with full to partial sunlight and can be planted in rain gardens, cut-flower gardens, beds, and borders, or near ponds and streams.

Size and method of spreading:

Blue flag iris is typically between 2 to 2 ½ feet tall and wide. Plants spread via underground root structures (rhizomes) and self-seeding. 

Native geographic location and habitat: (include C-value if appropriate)

Blue flag iris is native to the northeastern United States.

Attracts birds or pollinators: 

Blue flag iris attracts a number of beneficial bee species, butterflies, and hummingbirds. 

Leaf description:

Blue flag iris has long, flat leaves that primarily occur around the bases of the plants (basal leaves). The leaves tend to arch backwards. 

Flower description:

The flowers of blue flag irises rise above the leaves. Typical of iris flowers, blue flag iris has three large petal-like sepals, or falls, surrounding the three smaller petals, or standards. The falls have yellow blotches near the throat of the flower, surrounded by an area of white, which is also surrounded in bluish-purple toward the tips of the falls, then covered with prominent purple veins. The standards are approximately two-thirds the size of the falls, bluish-purple, and may also be covered in purple veins. The falls droop backward, and the standards may droop, spread, or stand erect. Emerging from the center of the standards are three spreading, light bluish-purple, petal-like structures (divided petaloid style) that cover the pollen-bearing structures (stamens).

Fruit description:

Blue flag iris produces fruit in the form of capsules. The capsules are oblong and have three adjoining, angled sides that split at maturity to release seeds. 

Plant Care:

Blue flag iris may tolerate partial shade, but will bloom best in full sun. Supplemental water is necessary when conditions are dry. Wearing gloves during division is recommended. 

List of pests, diseases, and tolerances:

Insect pests of blue flag iris include aphids, iris borers, and iris thrips. Blossom blight, leaf blight, and leaf spot are other diseases that may affect blue flag irises. Aphid pests can spread mosaic virus.


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