Purple loosestrife is a European plant probably introduced to the United States as an ornamental. It reproduces both by seed and creeping rootstocks. Infestations can impede water flow and replace beneficial plants, and thus displace wildlife. It can be found in shallow, marshy wetland areas and ditches.
Purple loosestrife is a semi-aquatic creeping herbaceous perennial growing 6 to 8 feet tall. There are five to seven petals on rose purple flowers that appear in columns along the upper end of stems. Leaves are lance shaped with smooth margins up to 5 inches long. Bloom is in midsummer.
Biocontrol is limited in availability but control can be good to excellent. Herbicides with an aquatic label can offer fair to good control.