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Yellow Flag Iris, Paleyellow Iris, Yellow Iris, Water Flag - Iris pseudacorus


Family: Iridaceae - Iris family Genus Common Name: Iris Native Status: IntroducedMonocot Perennial Herb
Iris pseudacorus - Yellow Flag Iris, Paleyellow Iris, Yellow Iris, Water Flag. Iris pseudacorus is a species brought in from Europe as a decorative plant for its attractive yellow flowers, escaped, and has established itself well in wet areas throughout much of North America. Think cattails for the habitat in which it grows. It has been used as a plant in natural sewage treatment since it can remove metals from waste water. Its propagation is restricted as an invasive weed in a number of states ranging from Massachusetts to Washington and California.

Found in:
AL, AR, CA, CT, DC, DE, FL, GA, ID, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MS, MT, NC, NE, NH, NJ, NV, NY, OH, OR, PA, RI, SC, TN, TX, UT, VA, VT, WA, WI, WV
Iris pseudacorus

Distribution of Iris pseudacorus in the United States and Canada:
USDA Map temporarily unavailable.
Blue=Native; Grey=Introduced

Map from USDA Plants Database:
USDA, NRCS. 2017. The PLANTS Database (http://plants.usda.gov, 16 Jan 2025). National Plant Data Team, Greensboro, NC 27401-4901 USA.

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Site: Boise Irrigation Canal, Ada County, ID Date: 2010-June-08Photographer: Cindy Williamson
Nikon D40
The lovely flowers of Yellow Iris are large and showy. This is the only yellow Iris in the United States.
Iris pseudacorus
Site: Boise RIver, Ada County, ID Date: 2011-June-11Photographer: Gerald C Williamson
Nikon D7000
This is typical Iris pseudacorus habitat - the edge of ponds, marshes, and other waterways. Although it prefers wet habitat, it is drought tolerant and the roots can survive for months without water. Yellow Flag will grow in dense clumps, spreading vegetatively by rhizomes and sexually via seeds. Both the leaves and the flowering stalk can be up to 4 feet tall.
Click on the photo for a larger image
Iris pseudacorus
References used for identification and information:
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Iris pseudacorus initially published on USWildflowers.com 2012-11-27; Updated 2015-06-24

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