Purple Loosestrife A Beautiful Yet Prohibited Invasive Species in New York

A large patch of Purple Loosestrife near Tops in Tannersville.

The New York State Department of Environmental Conservation (DEC) has taken a proactive stance in identifying and managing Purple Loosestrife (Lythrum salicaria) as a prohibited invasive species. Despite its striking beauty, this herbaceous perennial poses a significant threat to the state's ecosystems.

Growing between 3 to 7 feet tall, Purple Loosestrife is easily recognized by its vibrant magenta flowers, which bloom from July to September. The deep purple hue adds a touch of color to the landscape, making its invasive status all the more unfortunate, yet its beauty is undeniable.

The plant's journey to North America likely began as early as 1869, potentially via contaminated solid cargo ship ballasts, especially in the Great Lakes, including Lake Ontario. Purple Loosestrife may also have been imported deliberately as an ornamental plant or an herbal remedy for digestive ailments.

Invasive species like Purple Loosestrife can severely disrupt natural communities and systems. They out-compete native species, reduce biological diversity, alter community structures, and in some cases, transform entire ecosystems. The presence of invasive species threatens New York's agriculture, wildlife, fish, shellfish, landscaping, parks, gardens, recreation resources, and even the health of pets, animals, and humans. This urgent issue affects all New Yorkers.

The DEC maintains a comprehensive list of both prohibited and regulated invasive species. Prohibited species, including Purple Loosestrife, cannot be knowingly possessed, sold, imported, purchased, transported, or introduced. Conversely, regulated species cannot be introduced into a free-living state but can be legally possessed, sold, bought, propagated, and transported.

To control the spread of Purple Loosestrife, the DEC recommends several management strategies:

Biological Control: The DEC may release beetles and weevils native to Europe and Asia to suppress the growth and reproduction of Purple Loosestrife. The leaf-eating beetles Galerucella calmariensis, and G. pusilla target the leaves and new shoots, while the weevils Nanophyes marmoratus and Hylobius transversovittatus consume seeds, flower buds, roots, and foliage. These insects are most effective when released in the summer during the loosestrife's active growth period.

Chemical Control: Glyphosate herbicides can manage Purple Loosestrife, but an aquatic formulation is necessary for treatments near or on water. Spraying should be performed in the summer when the plants are flowering.

Mechanical Control: Mowing or cutting can prevent Purple Loosestrife from flowering, although it will not kill the plants. Small or light infestations can be eradicated early in the season.

Despite its invasive nature, the Purple Loosestrife's purple palette holds a certain charm, especially during the dog days of summer. Its contrast with the Yellow Goldenrod, green grasses, and blue skies brings many smiles, reminding us of the warm days we yearn for in the depths of winter.

Though it is one of many invasive species in New York State, the beauty of Purple Loosestrife is undeniable, even as efforts continue to manage its spread and protect the local ecosystems.