Page authors: Don Knoke, David Giblin
Iris missouriensis
western blue flag, Rocky Mountain iris

Distribution: Occurring chiefly east of the Cascades crest in Washington, but also known from the Puget Sound area; British Columbia to California, east to the Rocky Mountains.

Habitat: Common in vernally moist meadows, especially in sagebrush and Ponderosa pine forests.

Flowers: May-July

Origin: Native

Growth Duration: Perennial

Conservation Status: Not of concern


Herbaceous perennials from thick rhizomes, the simple flowering stems 2-4 dm. tall, leafless.


Leaves basal, linear, 2-4 dm. long and 5-12 mm broad.


Flowers usually 2, pale to deep blue, purple-lined, subtended by a pair of involucral leaves; pedicels stout, up to 6 cm. long; perianth parts fused in a tube at the base, the tube 5-8 mm. long; sepals 3, oblanceolate, 5-6 cm. long, spreading and reflexed; petals 3, shorter and narrower than the sepals, erect; stamens 3, opposite the sepals; style branches 3, 20-25mm. long, with 2 terminal lobes about as long; stigma broad and slightly notched; ovary inferior.


Capsule 3-celled, spindle-shaped, leathery, 3-5 cm. long.

Accepted Name:
Iris missouriensis Nutt.
Publication: J. Acad. Nat. Sci. Philadelphia. 7: 58. 1834.

Synonyms & Misapplications:
(none provided)
Additional Resources:

PNW Herbaria: Specimen records of Iris missouriensis in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Iris missouriensis checklist entry.

E-Flora BC: Iris missouriensis atlas page.

CalPhotos: Iris missouriensis photos.

USDA Plants: Iris missouriensis information.

65 photographs:
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