Purple loosestrife has woody, square stems with purple flowers at the ends.
Purple loosestrife stems are four to ten feet tall, hairy, woody, and angled (four to six sides). Leaves are green and sword-shaped with a round or heart-shape at the base and are whorled or paired around the stems. Flowers are pink-purple with five to seven narrow petals around a yellow center. There are many flowers along the top six to 12 inches of the flower spikes. Purple loosestrife blooms July through September.
Every purple loosestrife plant can produce up to 2.7 million seeds each year. Because flowers bloom gradually on the stalk, seeds are produced and released for multiple weeks. The seeds are as small as grains of sand and thus easily spread by wind, water, animals, and humans. Loosestrife seeds often germinate right away, but they can lay dormant for multiple years before they sprout. Purple loosestrife looks similar to native fireweed and blue vervain, which are beneficial wetland plants.
Purple loosestrife has spread across North America.
Mostly seeds, some rhizomes