War on Weeds—weeds are everybody’s problem
Photo courtesy of Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
THE ISSUE: Yellow flag iris
Yellow flag iris (Iris pseudacorus) is an aquatic perennial native to Europe and the Mediterranean area. It was originally introduced as an ornamental but has since escaped. It invades areas along canals, ponds, lakes, or rivers. Its presence damages native environmental conditions and reduces water flow. Don’t be fooled by its large showy flowers, it’s a weed that can be very difficult to eradicate!
Yellow flag iris can grow up to 4 feet tall. Prior to flowering it looks a lot like a cattail. Leaves are long, slender, pointed at the tips, and have a mid-rib. It has large yellow flowers that have a peculiar shape. Unfortunately, this weed can spread by rhizomes and seed. Thick rhizomes allow this weed to form dense mats of vegetation that choke out native plants, block light, change habitat, and reduce the flow of water.
Integrated Pest Management (IPM) Options:
• Prevention— Learn to identify this plant. Never transport unknown plant material. Always plant clean seed!
• Mechanical— Hand digging or pulling can be effective on small infestations. Remove as much plant material as possible. Broken rhizomes can root and form new plants. Wear protective clothing when handling this weed, it’s sap is poisonous and can cause skin reactions. Removing seed pods can help reduce the spread of this weed.
• Chemical—Extreme care should be taken when using herbicides near a body of water. Always read and follow herbicide label directions! Glyphosate and Imazapyr are two herbicide active ingredients that can be effective at controlling this weed. Both active ingredients are non-selective, meaning they will kill or damage other plants as well. Consult local authorities for more information related to controlling this weed.
Justin Hatch, University of Idaho Extension Agriculture Educator in Caribou and Bear Lake Counties. 208-547-3205 [email protected]
