Bloomipedia
Western blue flag (Iris missouriensis)
Photo: Deniz Wilson via iNaturalist · CC0 · resized

Flower profile

Western blue flag

Iris missouriensis

Native in the lower 48

Western blue flag is a wildflower that USDA PLANTS lists as native in the lower 48 states. It's on our flower lists for 4 states, and across the U.S. it's most often seen in bloom in May–July.

15states
4of our state lists
10,686U.S. sightings*

*iNaturalist research-grade observations, as of October 17, 2026.

On our lists for: Colorado, New Mexico, South Dakota, Wyoming

Quick look

Iris missouriensis is a hardy flowering rhizomatous species of the genus Iris, in the family Iridaceae. Its common names include western blue flag, Rocky Mountain iris, and Missouri flag.

  • It belongs to the Iridaceae family. iNaturalist
  • USDA PLANTS describes it as an herb (forb) with a perennial life cycle. USDA PLANTS
  • USDA PLANTS lists it as native in the lower 48 states and records it in 15 states. USDA PLANTS
  • NatureServe lists it as native to Colorado, New Mexico, Wyoming and South Dakota. NatureServe
  • In Colorado, most iNaturalist sightings of it in flower come in May–July. iNaturalist
  • In New Mexico, most iNaturalist sightings of it in flower come in May–July. iNaturalist
  • USDA PLANTS lists its flower color as purple. USDA PLANTS
  • USDA PLANTS gives its bloom period as spring. USDA PLANTS
  • USDA PLANTS lists a mature height of about 1 ft. USDA PLANTS
  • iNaturalist has 3,006 research-grade sightings of it in Colorado, ranking #47 among the 110 flowers on our Colorado list. iNaturalist
  • iNaturalist has 1,442 research-grade sightings of it in New Mexico, ranking #27 among the 109 flowers on our New Mexico list. iNaturalist
  • iNaturalist has 355 research-grade sightings of it in Wyoming, ranking #82 among the 107 flowers on our Wyoming list. iNaturalist

Western blue flag gift ideas

Handmade western blue flag gifts from independent makers.

🌱 Sample spot. Handmade gift picks from independent shops will appear here once our shop partnership is approved. These cards are placeholders, not real products.

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When does it bloom?

Flowering records by month across the U.S. (iNaturalist research-grade observations marked “Flowering”) (584 records)
Bloom time in each of our 4 states
StateTypePeak bloomSightings*
ColoradoNativeMay–July3,006
New MexicoNativeMay–July1,442
WyomingNativefew records355
South DakotaNativefew records312

Conservation status

Federal (U.S. ESA)
Not listed Not listed under the Endangered Species Act. USFWS ECOS does track it with the label “Species of Concern,” which is informal and gives no legal protection. USFWS ECOS
NatureServe global
GNR Not yet ranked worldwide. NatureServe
Colorado
No list Colorado has no state law listing endangered or threatened plants, so we show NatureServe's Colorado ranks instead. NatureServe: SNR, not yet ranked in Colorado.
New Mexico
Not listed Not on New Mexico state endangered plant species (19.21.2.9 NMAC). NatureServe: SNR, not yet ranked in New Mexico. 19.21.2.9 NMAC
Wyoming
No list Wyoming has no state law listing endangered or threatened plants, so we show NatureServe's Wyoming ranks instead. NatureServe: S4, apparently secure in Wyoming.
South Dakota
No list South Dakota's endangered and threatened list (ARSD 41:10:02) covers animals only, so we show NatureServe's South Dakota ranks for plants. NatureServe: SNR, not yet ranked in South Dakota.
Rare elsewhere
No other U.S. state ranks it S1, S2, SH or SX.

Checked October 17, 2026. Rankings and lists can change, so follow the links for the latest.

Can you eat it?

For peopleNot well documented

None of the sources we checked (NC State Extension (no page for this plant), USDA PLANTS) say whether it's edible or poisonous for people.

For petsToxic to dogs, cats and horses

ASPCA's entry “Flag” (Iris species), which covers the whole genus, lists it as toxic to dogs, cats and horses. Signs include: Salivation, vomiting, drooling,lethargy, diarrhea. Highest concentration in… ASPCA

🌿 Never eat a wild plant unless you're certain of its ID; this isn't medical advice. Worried about a person? Call Poison Control at 1-800-222-1222. Worried about a pet? Call your vet.

Where does it grow?

USDA PLANTS records Western blue flag in 15 states.

recorded by USDA PLANTS on our state lists not recorded

See the full list of states

Arizona, California, Colorado, Idaho, Minnesota, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oregon, South Dakota, Utah, Washington, Wyoming.

Colorado counties with USDA records: Alamosa, Boulder, Conejos, Custer, Delta, El Paso, Elbert, Garfield, Grand, Gunnison, Huerfano, Jackson, Jefferson, La Plata, Lake, Larimer, Las Animas, Mesa, Mineral, Moffat, Montezuma, Park, Pitkin, Rio Grande, San Juan, San Miguel, Summit, Teller.

New Mexico counties with USDA records: Bernalillo, Catron, Cibola, Colfax, Lincoln, Los Alamos, McKinley, Mora, Rio Arriba, San Juan, San Miguel, Sandoval, Santa Fe, Socorro, Taos, Valencia.

Wyoming counties with USDA records: Albany, Big Horn, Carbon, Converse, Crook, Fremont, Hot Springs, Laramie, Lincoln, Natrona, Park, Sublette, Sweetwater, Uinta, Weston.

More Colorado flowers

Great mullein (Verbascum thapsus)

Great mullein

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Introduced

🌼 Blooms in CO: June–October
Blue columbine (Aquilegia coerulea)

Blue columbine

Aquilegia coerulea

★ CO state flowerNative

🌼 Blooms in CO: June–August
Showy milkweed (Asclepias speciosa)

Showy milkweed

Asclepias speciosa

Native

🌼 Blooms in CO: June–July

Sources