Yellowflag Iris


  • Dark green leaves in a fan-like arrangement
  • Three large downward facing yellow petals streaked with brown or purple streaks
  • Bright yellow, showy flower similar to common garden irises
  • Height 3 to 5 feet

Weed Pictures

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Weed Information

ToxicityToxic. Livestock, dogs, cats and humans.
ControlMechanical, cultural and herbicide. Contact your county weed district or local Applicator for more information.
HabitatAlong shorelines, ditches, stream banks, floodplains, forests, areas of shallow water, low-lying wetlands and fish ponds.
RootExtensive root system.
Leaf ShapeSword-like with smooth edges.
LifespanPerennial; two years or longer.
Priority 2A WeedCommon in isolated areas of Montana.
Similar Looking PlantsCattails or Rocky Mountain iris when it is not flowering.
Important InformationThis plant is currently sold as an ornamental. Each large seedpod can produce 120 seeds. Yellowflag is of two species of iris known to occur in Montana outside of horticultural plantings; the only yellow one.