Yellow Flag Iris

Strategy – This perennial plant that invades ditch banks, stream banks, and semi-moist meadows. This plant is considered a wild flower, but handles grazing which allows it to spread more efficiently. This plant has parallel running veins like most Iris’s and produces yellow flowers. It grows to a height of up to 4 feet tall, with basal leaves reaching a width of ½ inches. It spreads by branches of rhizomes as well as by seeds which can float down the waterway for up to 100 yards.

Attack – This plant spreads quite well in areas of minimal disturbance as it is not a preferred food source for livestock, in fact it has been known to be toxic to the animals (like the Iris’s in your front yard). Once established it becomes quite a nuisance and difficult to control.

Defense – Don’t let this PRETTY plant become a problem. Once you discover that it has spread away from your cultivation, it has become a weed. Although it is a rhizomatous perennial, it can be managed with a shovel. Because it thrives in moist areas it will generally have shallow roots, therefore when digging it up one does not have to go deep and the roots will be concentrated into small clumps. As no livestock will graze it, there is not animal control. Some herbicides are effective. Roundup can be effective at pre-bloom or in the fall or even try Habitat (BASF). If present in the pasture or meadow Escort® XP will be very effective when applied to the actively growing plant. Remember, not all pretty plants are always friendly. Call your County Weed Superintendent for proper identification.


Kali Sherrill, Twin Falls County Weed Superintendent, tells us why Yellow Flag Iris is such a nasty invader along our streams and canals in the Twin Falls area.

PLEASE NOTE – The proper use and application of herbicides can be an effective way to control and eradicate noxious and invasive plants. Before using herbicides, always carefully follow the label and safety instructions on the label. While we recommend the use of herbicides as one of the effective tools for integrated pest management, the Idaho Weed Awareness Campaign assumes no liability for herbicide applications.