Iris missouriensis Nutt.
Rocky Mountain Iris, Western Blue Flag
Iridaceae (Iris Family)
Synonym(s): Iris longipetala, Iris missouriensis var. arizonica, Iris missouriensis var. pelogonus, Iris pariensis, Iris tolmieana
USDA Symbol: IRMI
Rocky Mountain iris is slender-stemmed and 1-2 ft. high. One to four flowers occur per stem. The grayish-green leaves are relatively broad. Large, delicate, pale blue to lavender to white 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.
This species often forms dense, large patches in low spots in pastures, where the tough leaves are avoided by cattle.
From the Image Gallery
Plant CharacteristicsDuration: Perennial
Fruit Type: Capsule
Size Notes: Up to about 2 feet tall.
Bloom InformationBloom Color: White , Yellow , Blue , Purple
Bloom Time: May , Jun , Jul
DistributionUSA: AZ , CA , CO , ID , MN , MT , ND , NE , NM , NV , 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
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
PropagationSeed Collection: Easily collected from the large capsules.
Commercially Avail: yes
Find Seed or Plants
Find seed sources for this species at the Native Seed Network.
View propagation protocol from Native Plants Network.
Mr. Smarty Plants says
Native shade plants around fountain in California
March 18, 2009
Hi, we just put a fountain in our front yard. It is in a mostly shady area. I need to know what plants would go best around the fountain and survive in the shade.
view the full question and answer
National Wetland Indicator Status
From the National Organizations DirectoryAccording to the species list provided by Affiliate Organizations, this plant is on display at the following locations:
Santa Barbara Botanic Garden - Santa Barbara, CA
Tohono Chul Park, Inc. - Tucson, AZ
Native Seed Network - Corvallis, OR
BibliographyBibref 946 - Gardening with Prairie Plants: How to Create Beautiful Native Landscapes (2002) Wasowski, Sally
Bibref 841 - Native Alternatives to Invasive Plants (2006) Burrell, C. C.
Search More Titles in Bibliography
Web ReferenceWebref 38 - Flora of North America (2019) Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
Webref 23 - Southwest Environmental Information Network (2009) SEINet - Arizona Chapter
Additional resourcesUSDA: Find Iris missouriensis in USDA Plants
FNA: Find Iris missouriensis in the Flora of North America (if available)
Google: Search Google for Iris missouriensis
MetadataRecord Modified: 2023-02-14
Research By: TWC Staff