Iris tenax

From Puget Prairie Plants
  • Scientific Name: Iris tenax
  • Family: Iridaceae
  • Common Names: Oregon flag, tough-leaf iris
  • Codon: IRITEN

Photo by Rod Gilbert, also featured on Main Page


Scientific classification
Kingdom: Plantae
Subkingdom: Viridiplantae
Phylum: Tracheophyta
Subphylum: Spermatophytina
Class: Magnoliopsida
Subclass: Lilianae
Order: Asperagales
Family: Iridaceae
Genus: Iris L.
Species: Iris tenax Douglas ex Lindl.



Clump-forming herb growing from branched rhizomes, up to 3 dm tall.[2] Stems are solid.[3]

Basal leaves reach up to 45 cm, cauline leaves reduced, more or less erect, up to 15 cm. long, sheathing the stem for up to half their length.[2]

Sepals (the outer 3 segments, reflexed, sometimes referred to as "falls",) have pronounced veination and usually bearing a yellow "signal". Style branches, petalloid, opposite sepals and curved over them.[3] Ovary inferior.

Fruit is an oblong, 3-sided capsule, 3-5 cm long.[2]

Genus name comes from Greek Iris, rainbow.[3]

Bloom Period

June - August[4]


Grays Harbor County and south Puget Trough, Washington, southward in western Oregon, to northwest California.[3]


Prairies, meadows, and open woodlands, lowland to upper montane zones.[3]


Tolowa Dee-ni’ use to make cordage.[5]

There are several uses of the root in herbalism, but fresh root preparations are extremely harmful. Preparations should only be made with the completely dried root, and administered by a skilled herbalist, as even fresh preparations are low-dose.


Iris tenax does not spread quickly, but will form large clumps of underground bulbous stems. It requires wet soil in the spring time and well drained soil during the drier months.[6]

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  1. Integrated Taxonomic Information System. Retrieved from
  2. 2.0 2.1 2.2 Bowcutt, F., & Hamman, Sarah. (2016). Vascular plants of the South Sound prairies (First ed.). Olympia, Washington: The Evergreen State College Press.
  3. 3.0 3.1 3.2 3.3 3.4 Hitchcock, C. L., Cronquist, A., Giblin, D., & Legler, B. et al. (2018). Flora of the Pacific Northwest: an illustrated manual. Seattle: University of Washington Press.
  4. WTU Herbarium, Burke Museum, & University of Washington. Retrieved from
  5. Baker, Marc A., 1981, The Ethnobotany of the Yurok, Tolowa and Karok Indians of Northwest California, Humboldt State University, M.A. Thesis, page 33. Retrieved from