At this time of year, I spend a lot of time traveling between the Conservancy's preserves. 

While driving around the region, I am always distracted by the purple flower I see growing along most local streams and almost every wetland.  A beautiful flower but very aggressive invader, Purple Loosestrife is a perennial weed native to Europe and Asia that was introduced to the U.S. in the 1800s.  Purple loosestrife destroys natural habitats by displacing native vegetation which, in turn, results in the displacement of native wildlife that utilized such vegetation for food and shelter.

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In order to control purple loosestrife, you first need to ensure you are identifying the plant properly. The leaves are downy with smooth edges and are arranged in pairs opposite one another along the stalk.  For very small infestations of just several plants, I would recommend pulling or digging up each plant and discarding of it in a tightly closed bag or other container. Mature plants pose the biggest problem because their rootstock is extensive and can send up numerous shoots, making early detection and rapid response imperative.  If an infestation is rather extensive, chemical control will be necessary.  Because loosestrife grows most often in ecologically sensitive wetlands, chemical control is best conducted by a licensed herbicide applicator.

Beginning in 1996, insects were released for the control of purple loosestrife in twenty-five U.S. states and seven Canadian provinces.  The agents released include two species of leaf-eating Galerucella beetles, a root-boring weevil, and two flower-eatingNanophyes beetles. While complete eradication cannot be expected from the use of any biological control agent, the goal is to significantly impact the populations of purple loosestrife and reduce them to a more manageable size. This will hopefully occur within the next 15-20 years.

In most states, purple loosestrife is listed on the noxious weed list and is illegal to sell.  However, it is still available for sale at many locations in Pennsylvania.  We encourage you not to buy it and to look instead for native alternatives such as Joe-pye weed, blue vervain, New York ironweed, monkey flower, blazing star and lobelia.