Purple Loosestrife (Lythrum salicaria)

Key Identification Features

Description

Purple Loosestrife is an invasive and a distinctive roadside plant that is disruptive to wetland ecosystems across New York State. L. salicaria produces pink, purple or magenta flowers, which are tiny and organize themselves onto a spike that shoots straight up from July to September. The entire plant is also quite straight and emerges in a branching pattern from the base. Many stems can emerge from a singular root-base, giving the plant a “bushy” appearance. The long, straight leaves usually arrange in an opposite pattern along the square stem, although they can also appear in whorls or alternate positions. Reaching between 3 and 7 feet, this invasive is tough to miss.

Native Range

Native to Eurasia, Purple Loosestrife arrived in the U.S. by the mid-1800’s. Adored for its attractive purple flowers, L. salicaria has been used as a decorative, ornamental plant in gardens throughout the country. It has also historically been used as a medicinal plant and a hide-tanning agent.

Habitat and Dispersion

Purple Loosestrife is an aggressive wetland invader in New York State. It is a perennial that thrives in moist soil, such as wetlands, pond-sides, stream and river banks, along roadside ditches, and additionally has the ability to survive in drier soils. This plant thrives in full sun, but can tolerate partial shade as well. Now established throughout almost every state in the U.S. and into Canada, Purple Loosestrife is successful in its insect pollination and seed dispersal tactics. The individual plants produce up to 2 million seeds that are spread via wind, or human activity.

Best Management Practices

The best way to avoid the spread of L. salicaria is to avoid planting it, or to detect its presence early. Since its spread is so aggressive, removing the plants when they are in small numbers is most ideal. For small infestations, hand pulling can be effective between June and August, before the plant goes to seed. Larger infestations, especially near drainage ditches, can also benefit from hand pulling, or cutting. It is important to prevent these seeds from spreading through the waterway. Chemical measures can also be taken, with wetland approved herbicides and/or the help of an herbicide professional. Some biocontrol beetles have been approved by the USDA for very large infestations.

Additional Resources