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December 07, 2016
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A purple problem

Purple loosestrife has a long flower head and is able to disperse thousands of seeds from a single head. The stem of purple loosestrife has a square cross section, and the corner edges can be felt when handled. (TRR photos by Scott Rando)

August 20, 2014

A few years back, some friends and I went to a seafood restaurant in eastern Long Island for dinner. As we walked through the entrance, I noticed a rectangular planter in which were growing some pretty purple flowers. These flowers caught my eye for a different reason though; they were all of the invasive plant species purple loosestrife (Lythrum salicaria). Perhaps the owner or an unwitting landscaper saw the pretty flowers along a roadside and decided to transplant them, not knowing the undesirable qualities of this plant.

Indeed, purple loosestrife was used in the past as an ornamental flower in garden environments. It was thought to be first introduced in the U.S. in the 1800s from soil that was used as ship’s ballast. This invasive plant spread naturally from seaports and also escaped from cultivation in gardens, where it is now present in all 48 contiguous states except Florida. The heaviest infestation is throughout the Northeast, extending westward across the upper Mississippi River valley to portions of the upper Midwest.

Purple loosestrife is present throughout our region, and it is in full bloom now. It prefers wetlands, shoreline areas, roadsides, and fields. Its invasive quality is that it will displace native species present. Areas overtaken by purple loosestrife suffer from habitat degradation when food plants used by other species are pushed out and are no longer present. Soil erosion into waterways may also increase as the more efficient soil-retaining native species of plants are no longer present.

Purple loosestrife is easy to spot now, with its purple flowers at the top of the stem. If a few plants are found on your property, they can be pulled out by the roots. A shovel may be needed for larger plants that are well rooted. Dispose of the plants, or at least the flower/seed heads, so the seeds do not spread. Seeds may lie dormant for several years if underwater, so there may be repeat growth the following year in some areas. Herbicides may be necessary for large infestations; a licensed applicator should be used, especially near water.