The Purple Loosestrife (Lythrum salicaria)

Description and Habitat

Purple loosestrife is an erect, perennial herb that grows from 0.5 to 3 meters tall depending on habitat conditions. It has a square, wooded stem and opposite or whorled leaves that are mainly lance-shaped. At the base of the plant the leaves are heart-shaped or rounded. The length of the leaves varies from 3 to 10 cm. Leaves at the base and inside of flower spikes tend to be smaller and attached alternately. The upper section of the purple loosestrife is generally covered with short hairs. In the summer the plants produce lush magenta-colored flowers. The purple loosestrife Purple loosestrife occurs widely in wet habitats, such as marshes, bogs, pannes, fens, sedge meadows, and wet prairies, but it also occurs in roadside ditches, on river banks, and at the edges of reservoirs.

Why is it a threat? What can we do to control the species?

Purple loosestrife invades various wetlands, such as: freshwater wet meadows, tidal and non-tidal marshes, river and stream banks, pond edges, reservoirs and ditches. It crowds out at least 44 kinds of native grasses, sedges and other flowering plants that offer higher-quality nutrition for wildlife. The plant confines native wetland plant species including some federally endangered orchids and swamp rose mallow, and it reduces habitat for waterfowl. This decreases the biodiversity of these ecosystems and replaces food sources for many organisms. Mechanical, biological and chemical removal options exist. The size and location of the invasion determine the control methods. Eliminating all the roots and underground stems of the plant by digging is mechanical removal, which is most effective with small, young invasions. Drying and burning or composting in an enclosed area will dispose of the plants efficiently.Herbicides chemically control purple loosestrife in areas too large to manage by digging. Biological control is considered the most effective control method for large invasions and long-term treatment. Galerucella pusilla and Galerucella calmariensis are two bio-control insect species that have been the most successful in the treatment of purple loosestrife.