Family: Iridaceae (Iris Family)
Duration and Habit: Perennial Herb
An herbaceous perennial in the Iris family (Iridaceae) growing to a height of 3 - 4 feet. The broad, sword-shaped leaves are stiff, erect, and green with a grayish-blue cast. The leaves are 1.6-3.3 feet long and 0.4-1.2 inches wide and have a central ridge on both sides of the blades. Flowers are white to cream or often yellow, borne on erect peduncles with several flowers on each stem and bloom from April- June. The fruit capsule is 6-angled, egg-shaped, and contains around 120 seeds that start out white then turn pale brown. Seeds are buoyant and can be dispersed over long distances by water. The rhizomes are pink- fleshed, and 0.4-1.6 inches in diameter and may extend vertically 4 to 8 inches deep.
Ecological Threat: Yellow iris has been widely planted around the world as a showy garden or pond ornamental plant and has escaped intentional plantings. It is a rather large plant with strong competitive abilities. It can form dense colonies and impenetrable thickets in fresh or brackish water displacing native species and altering habitat for animals. All parts of the plant are poisonous.
Biology & Spread: Spreads vegetatively through the break-up of rhizomes or from abundantly produced seeds.
History: Introduced for ornamental wetland habitats, for erosion control or to remove metals in sewage treatment plants, as it is effective at removing nutrients and trapping sediments.
U.S. Habitat: Pale yellow iris can survive a range of environmental conditions. It grows in fresh or brackish water often occupies habitats that have low oxygen. It can be found in wetlands, shorelines, rocky shores, ditches, stream-banks, floodplain forests, and areas of shallow water. Yellow iris will tolerate high soil acidity (pH from 3.6-7.7) and requires high levels of nitrogen for optimum growth.
U.S. Nativity: Introduced to U.S.
Native Origin: Western Asia, North Africa; western Europe, N. Africa (Bailey, L.H. and E.Z. Bailey, Hortus Third: A Concise Dictionary of Plants Cultivated in the United States and Canada, MacMillan Publishing Co., Inc., New York , (1977).); NatureServe Explorer
U.S. Present: AL, AR, CA, CT, 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
Distribution: Newfoundland and Minnesota southward, widely established.
List All Observations of Iris pseudacorus reported by Citizen Scientists
Manual- Caution should be used if pulling out this plant because it can cause skin irritation; remove seed pods to help control population expansion; dig up small infestations; remove entire rhizome root system; use chopping machines for larger infestations; burn where conditions allow.
Chemical- It can be effectively controlled using any of several readily available general use herbicides such as glyphosate that is approved for wetland habitats. Follow label and state requirements.
Czarapata, Elizabeth J., Invasive Plants of the Upper Midwest, an Illustrated Guide to their Identification and Control, 2005. P. 110-111
Aquatic Plant Information System (APIS): Iris pseudacorus L. (Pale Yellow Iris)
USDA Forest Service, Forest Health Staff, Newtown Square, PA. USDA Weed of the Week - http://www.na.fs.fed.us/fhp/invasive_plants/weeds/yellow-iris.pdf
Google Search: Iris pseudacorus
Google Images: Iris pseudacorus
NatureServe Explorer: Iris pseudacorus
USDA Plants: Iris pseudacorus
Invasive Plant Atlas of the United States: Iris pseudacorus
Bugwood Network Images: Iris pseudacorus