Serving Montana Agriculture and growing prosperity under the Big Sky

Yellowflag Iris

(Iris pseudacorus)

Yellowflag Iris

(2A, common in isolated areas of Montana)

(Iris pseudacorus)

Quick ID

  • Yellow flowers with 3 downward-pointing sepals and 3 upward-pointing petals
  • Rhizomes contain black sap
  • Plants are often 3 to 5 feet tall
Yellowflag Iris Location Map

Map Courtesy of Montana Natural Heritage Program, Yellowflag Iris – Low Suitability: 9% of Montana, Moderate: 2%, Optimal: 2%. Larger image.

yellowflag iris plant
Yellowflag Iris Plant

Video Information

Weed Images

Yellowflag Iris plant
Yellowflag Iris flower
Yellowflag Iris leaf
Yellowflag Iris Seed
Yellowflag Iris stem
Yellowflag Iris Rhizome - Photo by Leslie J. Mehrhoff, University of Connecticut,
Yellowflag Iris Invading - Photo by Graves Lovell, Alabama Department of Conservation and Natural Resources,

Weed Specifications

Weed Info
Type Information
Toxicity All parts of the plant are toxic to animals and can also cause severe skin irritation and allergic reactions in humans
Best Management Practices

Small clumps can be dug out but it’s only effective if the entirety of the rhizomes are removed, repeated mowing can help, specialty aquatic herbicides can be used with proper care

*See additional documents below
Habitat Shorelines, ditches, streambanks, floodplains, areas with shallow water, low lying wetlands, moist meadows
Root Rhizomes that form dense mats
Leaves Linear, sword-like, erect, flat, bright green, raised midrib, emerge from the ground in a fan-like arrangement
Lifespan Perennial
Similar Looking Plants Rocky Mountain iris, but Rocky Mountain iris has blue to lavender flowers and is a smaller plant, and cattail, which has round leaf bases, instead of the flat leaf bases yellowflag iris has
Important Information Established throughout most of the US, escaped ornamental that is still escaping and is often transplanted by homeowners, reproduces from rhizomes and seeds and seeds can be spread long distances with water flow, changes ecology by capturing sediment, chokes out beneficial vegetation, clogs irrigations systems and streams and can narrow waterways

Become a Early Detection, Rapid Response Partner

Report the Weed

Find Out More...

To Report, Contact: