pale yellow iris, yellow flag iris: Iris pseudacorus (Liliales: Iridaceae): Invasive Plant Atlas of the United States

pale yellow iris, yellow flag iris	USDA PLANTS Symbol: IRPS U.S. Nativity: Exotic Habit: Aquatic Plants
Iris pseudacorus L.

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Taxonomic Rank: Liliopsida: Liliales: Iridaceae
Synonym(s): paleyellow iris
Native Range: western Asia, North Africa; western Europe, N. Africa (BAIL);
Appearance Iris pseudacorus is a herbaceous perennial that can grow up to 3-4 ft. (0.9-1.2 m) in height. Foliage Broad, sword-shaped leaves are stiff, erect and glaucous. They measure between 1.6-3.3 ft. (0.5-1 m) long and 0.4-1.2 in. (1-3 cm) wide. Rhizomes are pink-fleshed and 0.4-1.6 in. (1-4 cm) in diameter. Flowers Flowers are showy and bloom from April to June. Usually yellow, their color can range from nearly white to cream. Flowers are 2.75-3.5 in. (7-9 cm) wide. They are borne on erect peduncles with several flowers per stem. There are six perianth clawed segments. Three of these are upward-pointing petals and three are down-ward spreading sepals. Sepals often have purple, brown or red veins on their yellow surface. Fruit Fruits are 1.6-2.7 in. (4-8 cm) long capsules. The capsules are 6-angled and cylindric-prismatic to ellipsoid. The average capsule contains about 120 white seeds that harden and turn brown as they mature. Ecological Threat It forms large clonal colonies displacing native species. The rhizomes are able to survive heavy droughts. Rhizomes and seeds can be transported downstream, further spreading the plant. Seeds can germinate even after a wetland area burns. It contains glycosides, making it toxic to grazing animals. No birds are known to disperse the seeds of this plant. Caution should be used when hand-pulling, as it can cause skin irritation.

Identification, Biology, Control and Management Resources

Element Stewardship Abstract - The Nature Conservancy
Weed of the Week - USDA Forest Service
Fact Sheet - Ontarios Invading Species Awareness Program

Selected Images from Invasive.org

View All Images at Invasive.org

Plant(s); in flower Todd Pfeiffer, Klamath County Weed Control, Bugwood.org Additional Resolutions & Image Usage	Flower(s); Nancy Loewenstein, Auburn University, Bugwood.org Additional Resolutions & Image Usage	Flower(s); Nancy Loewenstein, Auburn University, Bugwood.org Additional Resolutions & Image Usage	Fruit(s); fruit. Joseph M. DiTomaso, University of California - Davis, Bugwood.org Additional Resolutions & Image Usage
Flower(s); pale yellow form Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Flower(s); Nancy Loewenstein, Auburn University, Bugwood.org Additional Resolutions & Image Usage	Fruit(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Plant(s); along drainage area Nancy Loewenstein, Auburn University, Bugwood.org Additional Resolutions & Image Usage
Plant(s); along drainage area Nancy Loewenstein, Auburn University, Bugwood.org Additional Resolutions & Image Usage	Infestation; Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Seed(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Seed(s); Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org Additional Resolutions & Image Usage
Root(s); Inside of cut rhizome Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Root(s); large rhizome. Joseph M. DiTomaso, University of California - Davis, Bugwood.org Additional Resolutions & Image Usage	Plant(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Plant(s); Britton, N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada. Vol. 1: 540. USDA NRCS PLANTS Database , USDA NRCS PLANTS Database, Bugwood.org Additional Resolutions & Image Usage
Plant(s); USDA NRCS. Wetland flora: Field office illustrated guide to plant species. USDA Natural Resources Conservation Service. USDA NRCS PLANTS Database , USDA NRCS PLANTS Database, Bugwood.org Additional Resolutions & Image Usage

EDDMapS Distribution:
This map is incomplete and is based only on current site and county level reports made by experts and records obtained from USDA Plants Database. For more information, visit www.eddmaps.org