Rocky Mountain Iris

Rocky Mountain Iris, also known as Western Blue Flag, grows in western wet meadows, marshes, and along stream banks ranging from low valleys to alpine areas up to 9000 feet.   It spreads from a rhizome, frequently forming dense, large patches.  Flowers are born on slender stems, 1-4 per stem, and range from pale blue to blue-violet.

Its scientific species name, missouriensis, comes from the fact that Lewis and Clark collected Rocky Mountain Iris along the Missouri River in 1806.  Native peoples are known to have used its fine but strong and flexible fibers to make fishing nets, snares for game animals, string, and rope.  The rhizomes of the plant have both external and internal medicinal uses.

Rocky Mountain Iris is considered a noxious weed when it grows in the low spots of pastures, because its tough and bitter leaves are avoided by cattle.

In the garden Rocky Mountain Iris does best in medium textured soils with a neutral pH.   It is a long-lived plant requiring minimal maintenance.  It will spread to form a colony, so may need to be divided regularly once established.  Iris flowers attract both pollinating insects and hummingbirds.  Gardeners should note that whether fresh or dried, the seeds, rhizomes, and roots of Rocky Mountain Iris can cause minor skin irritation.  These same parts are mildly toxic if ingested, potentially causing fever and general gastric distress.