Purple Loosestrife

This is the time of year when I realize the impact that a beautiful but deadly plant has had on our Great Lakes Region. The beautiful killer is known as Lythrum salicaria, or commonly, Purple Loosestrife.

Purple Loosestrife is an invasive, non-native plant that was introduced to the North American continent from Europe in the 1800's. It is a most attractive plant, and until recently, was readily available for purchase in many local garden centers and mail order catalogs. Many states and provinces have banned the sale or importation of Loosestrife.

The main problem with Loosestrife is that while it may be well behaved in the average home garden, it wreaks havoc with the environment. It is well adapted to wetlands, and in fact, is one of the scourges of wetlands and farmland.

Purple Loosestrife chokes out existing wetland plants, and ruins the biodiversity of the wetlands. Many animals that occupy the wetlands and depend upon wetland plants for food sources are displaced when Loosestrife takes over. It is extremely vigorous and extremely difficult to eradicate.

Chemical controls do work, but only limitedly. The use of chemical eradication is a double-edged sword. Chemical control might eliminate the Loosestrife, but can also harm the other plants and wildlife in an area. It is best used on small stands of Loosestrife.

When Loosestrife came to this continent, none of its natural enemies were imported with it. There has been promising advances in biological control by the introduction of its nautral predators. Biological control consists of importing from Europe the insects that forage on Loosestrife, primarily Galerucella calmareisis L. and Galerucella pusilla Dufschmidt, two beetles that feed on the leaves of the plant. A weevil, Hylobius transvesovittatus, is a control insect that feeds on the root system of Loosestrife.

Educating the general public about this plant is one of the main ways that we can help to restrain this plant. If you have any Loosestrife in your garden, please eliminate it. It might be well-behaved in a home garden situation, but it can escape to cause problems. Even if the plant remains in situ, the pollen of Loosestrife, even the so-called sterile or "safe" varieties can cross with other varieties of Loosestrife to breed more seed. Pollinating insects and wind can disperse the pollen far and wide, and the seeds are easily dispersed on the wind. If you have the plant, please remove all parts down to the smallest root. Don't throw the plant on the compost pile, burn it or bag it up and let it die completely.

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