Purple Loosestrife is an herbaceous, wetland perennial. This pretty purple flower grows up to 2 meters tall with 30-50 stems that form wide-topped crowns. However, despite its aesthetic appearance, it is destructive to the surrounding environment. This plant overruns wetlands such as freshwater wet meadows, marshes, and the banks of rivers, streams, ponds, reservoirs and ditches. The wide-topped crowns that it forms dominate the environment and prevent native plants from growing, crowding out at least 44 native grasses, and flowering plants that support and nourish healthy ecosystems.
A single mature plant can produce up to 2 million seeds a year. So many seeds lead to vast, dense thickets, which are impenetrable and unable to be used as cover, food, or nesting sites for native wildlife. The bog turtle, black tern, and canvasback duck have been directly affected by the destructive invasions of Purple Loosestrife. This invasive plant demands an annual budget upwards of $45 million to restore habitats and control its spread. Purple Loosestrife also affects farmers and their land as it has a tendency to clog irrigation and drainage ditches, which leads to the loss of pastures and fields. This plant can be found in all of the contiguous United States, except Florida, and in every Canadian province; it covers approximately 400,000 acres federal land.
The removal of this plant can be very difficult, and it is important to remove all of the roots and underground stems to prevent regrowth. Digging up all of the plants and then burning or composting in an enclosed area is the most effective form of removal for small invasions by young plants. However, care must be taken to avoid small pieces of stems or seeds taking root and reestablishing the invasion. Large invasions are best controlled by long-term biological treatment. The black-margined loosestrife beetle, both adults and larvae, effectively reduce invasions of purple loosestrife over the course of several seasons by eating the flowers and leaves.