Purple loosestrife is a perennial plant that is native to Europe, Asia, Africa, and Australia. This plant can grow up to 2 meters high. The stems are reddish-purple and square. The leaves are lanceolate in shape, and they alternate in threes on the stem. The flowers are reddish-purple and contain a small fruit capsule with tiny seeds inside. When the plant is mature in the fall, the leaves turn bright red, and the stalks turn brown.