Bransford, W.D. and Dolphia
Iris missouriensis Nutt.
Rocky Mountain iris, Western blue flag
Iridaceae (Iris Family)
Rocky Mountain iris is slender-stemmed and 1-2 ft. high. One to four flowers occur per stem. They are pale to dark, lilac-purple and haves yellow bases. The grayish-green leaves are relatively broad. Large, delicate, pale blue or blue-violet flowers, often with purple veins, bloom at the top of stout, leafless (or with 1 short leaf) stalks that grow from dense clumps of flexible, tough, sword-shaped leaves.
The only native
species east of the Cascade Mountains and the Sierra Nevada, it often forms dense, large patches in low spots in pastures, where the tough leaves are avoided by cattle.
Image Gallery: 14 photo(s) available
Plant CharacteristicsDuration: Perennial Habit: Herb Leaf:
Green Fruit: Size Class:
Bloom InformationBloom Color: Purple
Bloom Time: May , Jun
AZ , CA , CO , ID , MN , MT , NE , NV , NM , ND , OR , SD , UT , WA , WY Canada: AB
, BC Native Distribution:
B.C. to s. CA (mostly e. of the Cascades), e. to the Dakotas, NM & Mex. Native Habitat:
Marshes; wet meadows; drier areas if moist until flowering time USDA Native Status: L48(N), CAN(N)
Growing ConditionsWater Use: High
Light Requirement: Sun
Soil Moisture: Wet
CaCO3 Tolerance: High
Soil Description: Wet soils.
Conditions Comments: This iris spreads to form colonies. It needs to be divided regularly.
BenefitUse Wildlife: Hummingbirds
Warning: POISONOUS PARTS: Rhizomes (thickened roots) and rootstocks, fresh or dry. Minor skin irritation when touched, low toxicity if ingested. Symptoms include nausea, vomiting, abdominal pain, diarrhea, elevated temperature following ingestion; skin irritation upon contact with seeds, rootstock, or cell sap. Toxic Principle: Irisin, iridin, or irisine. (Poisonous Plants of N.C.)
Conspicuous Flowers: yes