Lithrum salicaria L.
Purple loosestrife is a perennial introduced from Europe growing anywhere from 1-1/2-to-8-foot tall. The erect, square stem can be smooth-to-hairy and is multi-branched. The leaves are lance-shaped, entire, and are opposite or whorled. The magenta-colored flowers, which have five to seven petals, are arranged in long, vertical racemes.
Purple loosestrife can be found in moist, wetland sites and is highly invasive. Each plant can produce over 2.5 million seeds annually. If left unchecked, a wetland will eventually become a near monoculture of loosestrife. This plant poses a severe threat to waterfowl habitat and can impede water flow in irrigation ditches. Sometimes purple loosestrife is confused with fireweed (Epilobium angustifolium) and is still sold as an ornamental by many greenhouses and gardening retailers.
Currently, there has only been one infestation found in Teton County that had been planted as an ornamental; however, we know this weed species has been found in bordering counties. This invader could easily be introduced to any of the many lakes, private ponds, or rivers. Due to the severe threat that purple loosestrife poses to our waterways, fisheries, and wildlife, we are asking the public to please be on the look out for this weed species.
If you find this weed on your property or around Teton County, please report it immediately at 733-8419.