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Yellow Flag

Iris pseudacorus

Non-Native

Yellow Flag Locations in North America
Yellow Flag Locations in Southeast US
yellow flag diagram

yellow flag

USDA, NRCS. 2018. The PLANTS Database (http://plants.usda.gov, 28 March 2018). National Plant Data Team, Greensboro, NC 27401-4901 USA.
Illustration courtesy of University of Florida/IFAS Center for Aquatic and Invasive Plants. Used with permission.

What is Yellow Flag?

Physical Characteristics

Leaves:

  • Upright
  • Arching at the top
  • Flat
  • Grow from the soil
  • Sword-shaped
  • Thin
  • Pointed
  • 3-4 feet tall

Flowers:

  • Upright
  • 3-4 feet tall
  • Big
  • Showy
  • Yellow in color
  • Many flowers on each stem
  • 3 sepals pointing down
  • 3 small petals
  • 6 large petals
  • Sepals light brownish-purple veined

Fruit:

  • Seed pod
  • 1.5-3 inches long
  • 3 sided
  • Cylinder shaped
  • Green in color
  • Many seeded

Seeds:

  • Flat
  • Brown in color

Stem:

  • Thick rhizomes
  • 0.39-1.5 inches across

Roots:

  • 3.94-12 inches long

Where Does it Grow?

Non-Native

Yellow flag native to Europe. This plant can be found in marshes, wet savannas, pinelands, shallow water in ditches and in soggy meadows.

Is it Invasive?

Yellow flag is non-native to the United States, and it can be an aggressive invader that can cover large portions of land in a short period of time, and tends to disrupt the ecosystem by pushing the native species out of their habitat.

This plant is not native to North America, but has naturalized in much of the United States. While it is not illegal to possess this plant in Texas, it probably should not be introduced into new water bodies. 

How to Manage This Plant
Plant Glossary

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Photo Credits: The majority of the aquatic plant line drawings are the copyright of the University of Florida Center for Aquatic Plants (Gainsville). They are used with permission.

Aquatic plant photographs were provided by David Bayne, Jim Davis, Kelly Duffie, Billy Higginbotham, Michael Masser, John Clayton, Chetta Owens, Diane Smith, Joe Snow, Don Steinbach, Bridget Robinson Lassiter and Peter Woods.

You may use these photos, so long as you give credit to AquaPlant.

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