Yellow Flag Iris

Iris pseudacorus

YF flower
YF pod

Yellow Flag Iris - Perennial invasive ornamental that grows 2-3 feet tall, is considered toxic to herbivores and contains a skin-irritating sap.

Leaves: Broad, flat sword-shaped basal leaves that reduce in size going up the stem

Flower: Multiple flowers appear at stem terminals, can be pale to dark yellow, have 3 sepals and 3 petals with its petals shorter than its sepals. Blooms visible May - July.

Habitat: Grows in wetlands along the margins of lakes and slow moving rivers. It is most commonly found in shallow water or mud such as those in wet ditches.

Weed Classification: C Select

Why is it a Noxious Weed?
Due to its aggressive spreading and ability to form large rhizomatous clumps, Yellow Flag is very problematic in shallow water ways, irrigation canals, and ditches. Spread can happen easily through seed production and through rhizome fragmenting.

Control Recommendations:
WA State Noxious Weed Board
King County Noxious Weed Board - Best Management Practices
UC Davis Weed Report