Range: Common and widespread in most of western Oregon and southwest Washington west of the Cascade Mountains. There is a small separate population in northern California's Klamath Mountains.
Original material: Seeds sent to England by explorer-naturalist David Douglas 1825
Key identifying features:
Flower color: Wide color range from purple and lavender (near the Cascades), maroon or pink (southwest Washington and northwest Oregon), and pale blue to yellow, cream and white.
Habitat: Open or lightly shaded sites in open oak woodlands; unusual in coniferous forests except along the edges or where they have been logged over.
Name: By the British botanist John Lindley, from David Douglas' notes that local Indians used the tough ("tenax") leaf fibers as strong cordage to make nets, rope and snares.
Comments: This is the Pacific Coast native iris that most deserves a common name of "rainbow iris". Plants showing a wide range of colors can sometimes be found on a single small hillside. Before its extensive color gamut was well recognized, a yellow-flowered variety from the region of Henry Hagg Lake in northern Oregon was described as a separate species - Iris gormanii.
Wild tough-leaf iris forms large, attractive clumps. The species' cold hardiness could prove useful to hybridizers trying to develop attractive Pacifica strains that grow more easily in cooler regions elsewhere. Where their ranges overlap, I. tenax produces natural hybrids with I. douglasiana, I. chrysophylla, I. innominata, and in California probably with Iris tenuissima.
California's "Orleans Iris" comprises a small, isolated population along the Klamath River near the town of Orleans in Humboldt County. It was described in 1958 as a distinct subspecies - I. tenax klamathensis. The funnel-shaped floral tube is longer (around ½ to ¾ inch), flower color is limited to pale cream or light yellow with a yellow eye spot on the petals and reddish-brown veins, and it lives in more shaded habitats than the I. tenax populations farther north.