South Dakota Native Plant Research
Irdaceae : Iris missouriensis

Irdaceae : Iris missouriensis


Download Seed: The dark brown seeds of western blue flag are 4-4.5 mm long. (61 KB)

Download Mature plants (118 KB)

Family Name


Common Name

Western blue flag


Iris missouriensis is a rhizomatous perennial herb with erect, leafless. flower stalks (scapes) 25-60 cm tall. The basal leaves are linear, 25-45 cm long and usually less than 1 cm wide. The 1-2 flowers emerge from a spathe, 5-7.5 cm long. Each flower has 3 light to dark blue, spreading or reflexed sepals, 4-6 cm long, lined with purple and with a whitish blotch at the base, and three smaller, upright blue petals. There are 3 stamens opposite the sepals. The fruit is an oblong, 6 angled capsule, 5-8 cm long. Western blue flag blooms in June and July in wet meadows, along streambanks and open woodlands in western South Dakota.

Additional Notes

Western blue flag is an eye-catching addition to a moist native plant garden. The flowers are striking and attract hummingbirds.

Horticulture Notes

Seed Collection: Collect seed in late July to September when the pods turn brown, and the seeds are reddish brown in color.

Germination: The seeds need a 60-90-day cold stratification, or can be planted in the fall.

Vegetative Propagation: Division of rhizomes

Soils: Neutral to slightly acidic to alkaline soil

Light: Full sun to partial shade

Water: Prefer moisture, but once established will tolerate drier conditions.

Irdaceae : Iris missouriensis