Yellowflag Iris Flower
Introduction
Yellowflag iris, native to Europe, Great Britain, North Africa, and the Mediterranean region can be found almost everywhere in the United States. It is found in wetlands, along the edge of ponds, lakes, or slow moving streams or rivers and is fast becoming one of our most aggressive wetland bullies. This plant can grow in full sun or part shade. When it blooms in late spring to early summer it is unmistakable with its large pale to bright yellow iris flowers. The flowers look very similar to a garden iris but they are often streaked with brown to purple lines. Yellowflag is often mistaken for cattails when the blooms are not present. The best way to distinguish this plant when flowers are not out is to look for the large fruit pod in the summer or the fan-shaped plant-base other times of the year.
Concerns
Yellowflag is a popular wetland ornamental that is still sold on-line. It is very easily spread downstream of its original location both by broken off pieces of rhizome (roots) and by floating seeds. This plant forms incredibly dense stands connected by rhizomes. Several hundred flowering plants can be connected in one rhizome mass. These stands become so dense that they choke out all other native and beneficial wetland vegetation. The dense rhizome masses trap sediment, which reduces water flow affecting fish, plants, and animals. Yellowflag iris is toxic to livestock and other herbivores and the resins that it contains will cause skin irritation in humans.
Identification
This perennial has showy yellow flowers that resemble a typical garden iris. Each stem may have several flowers that each have 3 large downward facing yellow sepals that are streaked with brown or purple lines and 3 upward facing yellow petals. The plant including the flower stalk is 3-4 feet tall. The leaves are mostly basal and are folded around the stem in a fan-like fashion. The leaves will stay green until harsh winter weather begins.
What can you do?
Yellowflag iris is difficult to control both by mechanical means and with herbicide. When hand pulling or digging make sure to wear gloves because of the irritating resins and also make sure to get all pieces of the rhizome mass. One small fragment can start a new mass of plants. To use herbicides on yellowflag an aquatic license is required because of its proximity to water. If you have yellowflag iris on your property or you know where this plant can be found please contact your local county weed district.
Visit the MWCA Weed ID pages for additional information and pictures of yellowflag iris.
This series of articles was developed by Ravalli County. If you would like to use these articles please contact Ravalli County Weed District Weed Coordinator at (406) 777-5842.
Tags: Iris pseudacorus, noxious weeds, Priority 2A Weed, Yellowflag Iris