The flowers have five to six petals, are colored purple to magenta and vertically arranged on long spikes. It usually grows on moist or saturated soils. Older plants can form large masses of showy blossoms and look quite striking. In the fall, the leaves turn bright red for about 10 days, then turn brown and die back until the next growing season. Leaves, about two to four inches long near the base of the plant, are opposite to each other on the four to six-sided stem.
Leaves are long and narrow, with smooth edges.
A four to five-year old plant can have as many as 30 to 50 stems, grow up to 10 feet tall and five feet wide. Get rid of it, recommended Aldrich-Markham. If so, don't buy it. Inform the nursery that it has been designated a noxious weed by the Oregon Department of Agriculture, and therefore selling purple loosestrife in Oregon is illegal. To get rid of this noxious weed, Aldrich-Markham recommends digging out the plants while they are still young, making sure all the roots are removed.