Oregon Iris

If you have read our post on yellow flag irises, an invasive species here on the Washington coast, you might be wondering if there are any native iris species here. The good news is that there is one!

The Oregon iris (Iris tenax tenax), also known as toughleaf iris, is a perennial iris native to the Pacific Northwest. It can be found from southern Oregon to southern Washington west of the Cascades. Another subspecies, the Klamath iris (I. t. klamathensis), is endemic to the Klamath Mountains in northern California.

Compared to the invasive yellow flag iris, Oregon irises prefer drier soils. They need well-draining soils and will not tolerate standing water. Once established, they are drought tolerant. They prefer full sun to partial shade and low to mid elevations. They can typically be found in open areas such as prairies or meadows, disturbed areas such as roadsides or logged areas, and open woodlands.

The leaves are light green, upright, and narrow, only reaching about 5 millimeters broad and giving the leaves a grass-like appearance. Stems are also narrow. The stems grow to about 14 inches (36 cm) in height and the leaves can grow to be slightly longer.  

Oregon iris flowers are purple, lavender blue, pink, yellow, or white in color, though the latter is rare. The sepals have dark veining the same color as the rest of the rest of the flower and a yellow ridge (U.S. Forest Service, n.d.). Sepals reach about 3 inches (7.5 cm) in length (Mount Pisgah Arboretum, n.d.). There is usually only one flower per stem, but occasionally there are two. The plant blooms in mid to late spring.

Oregon irises propagate both by seed and by rhizome. Seeds are produced in oblong capsules that turn from light green to brown during the summer as the seeds develop. Seeds are light brown and wrinkled. Rhizomes are slow to spread and thus the plant will form compact clumps.

The flowers attract hummingbirds and other pollinators. They are deer and rabbit resistant. Like other species of iris, all parts of the plant can be toxic to pets and livestock. In humans, the plant can cause skin irritation when handled and symptoms such as nausea, vomiting, abdominal pain, and diarrhea if ingested (LBJ Wildflower Center, 2023).

The plant’s common name “toughleaf” and species name “tenax” (meaning “tenacious”) both refer to the tough fibers in the plant’s leaves. Native Americans used these fibers to make rope, string, and cording (LBJ Wildflower Center, 2023).

References

Oregon Iris. WSU Clark County Extension. (n.d.). http://pnwplants.wsu.edu/PlantDisplay.aspx?PlantID=588

Iris tenax ssp. tenax: Toughleaf Iris. U.S. Forest Service. (n.d.). https://www.fs.usda.gov/wildflowers/beauty/iris/Pacific_Coast/iris_tenax.shtml

Iris tenax. Lady Bird Johnson Wildflower Center - The University of Texas at Austin. (2023, February 14). https://www.wildflower.org/plants/result.php?id_plant=irte

Iris tenax. Mount Pisgah Arboretum. (n.d.). https://mountpisgaharboretum.org/learn/plant-list/iris-tenax/

© Laura Caldwell, June 2023