The Enemy: Creeping waterprimrose (Ludwigia peploides)
Strategy: Water primrose is a floating or emergent perennial plant that produces stems that grow up to 10 feet across the water. This plant is native to the southern coastal areas of the U.S. and can attack irrigation canals and ditches, as well, as the many hot springs in Idaho and its neighbors. It produces reddish stems and oblong leaves that may have reddish to white midveins. The leaf margins are generally smooth. It produces a yellow flower that extends above the leaves and stems above the water level.
Attack: Like many of our irrigation corridor invaders, this plant generally spreads by fragmentation during general maintenance activities. It can completely cover slow-moving waterways, marshes and springs. It has little food value for wildlife and displaces native and desirable plants. It can even affect the fish that inhabit the appropriate systems. It is common in the aquatic nursery trade, thus a possible invader.
Defense: If you have purchased this plant for your “ornamental” use and decide its not for you, dispose of it in the trash. If it is part of your fish aquarium and you don’t want to destroy the fish, do not throw it all into a hot-water stream to be “nice” to the fish and other species. Its harmful to the systems. Approved herbicides that work best and can be used over natural waters of the U.S. include Tricloypyr (Garlon/Vaslan/Aquasweep) and Imazapr (Habitat). Glyphosate (Aquaneet) can be used with good results. Irrigation waters are different. Proper identification is key to any weed control program. Call your local county weed department for more information.