A field of western blue iris (Iris missouriensis) is a beautiful sight. It is difficult to believe that this lovely native perennial is also considered a noxious weed in agricultural and range lands. The entire plant, especially the rootstocks, contains irisin, a toxic material. If eaten, western blue iris can be lethal. Bitter to the taste, livestock will not eat western blue iris unless starving. However, hay from pasture lands with heavy iris growth can cause problems.
Western blue iris grows in the western United States and western Canada, especially in the Great Basin. Although it grows in wet meadows and seepage areas in rangelands and along streambanks, this iris is drought tolerant. It only requires moisture in the spring and survives well when the land dries out later in the year.
Linear, grass-like, basal leaves grow from the western blue iris rootstock. The flowering stems are leafless and end in an inflorescence of one or two flowers. The dark blue to pale blue flowers have a long peduncle (stalk) below the ovary. Each blossom consists of reflexed (drooping) sepals and upright blue petals. The elongated sepals have a central yellow to orange stripe and diverging dark lines on a light background. The fruit is a large capsule.
Western blue iris is also commonly called flag, wild iris, or Rocky Mountain iris.
The Plains Indians used irisin as a poison on their arrow tips.
These western blue iris were in a field near the Hot Springs Campground at Hart Mountain National Wildlife Refuge (Oregon). Yes, there are hot springs nearby with a natural stone enclosure built by the CCC.