Yellow Flag Iris

Yellow Flag Iris

Iris pseudacorus

Information Sheet (PDF)

Watch List - Eradication Recommended

General

  • Family: Iridaceae
  • Introduced from: Europe and North Africa
  • An escaped ornamental

Habitat

  • Found in wetlands, along the edges of water bodies and waterways

Lifecycle

  • Perennial

Growth form

  • Semi-aquatic forb

Plant

Vegetation

  • Plant 3-6 ft tall 
  • Leaves overlap at the base, 35 in long and 1.25 in wide, sword shaped, dark green with a thickened middle
  • Usually 10 leaves per plant

Roots

  • Rhizomes form a “root ball” which can be several feet long and wide

Flower

  • May-July
  • Bright yellow
  • 3 upward curved petals and 3 downward curved sepals with brown to purple streaks
  • Multiple flowers along stem

Seed

  • Angled seedpods up to 3 in long
  • Up to 120 seeds per pod

Reproduction

  • Seed and Rhizomes

Similar Species

  • Garden iris varieties

Impacts 

Can crowd out native species and form large monocultures

Habitat and Distribution

  • General requirements: Wet habitat
  • Distribution: Limited in certain areas throughout Colorado and in Jefferson County

Control

Biological

  • None

Chemical

Cultural

  • Prevention - do not purchase, do not plant
  • Removal - Cut and bag flowers, dispose of in the garbage.  Do not compost

Mechanical

  • Burning - N/A
  • Grazing - N/A
  • Mowing - N/A


Use all chemicals according to the manufacturer’s label. No specific recommendation or endorsement is made or implied by listing methods or products.

Colorado Department of Agriculture - Yellow flag iris

Montana Weed Control Association - Yellow Flag Iris Video

USAD - Plants Profile for Iris pseudacorus (paleyellow iris)