When Boothbay resident Fran Gleason saw a questionable purple flower on her waterfront property, she thought something was off. Gleason is from Windham, where she said invasive purple loosestrife is prolific. She described herself and her husband as conservation and nature-oriented and she wanted to take quick action.  

“It happened to catch my eye, and I thought, gosh, I wonder if that's what's up here now,” she said. “... I just thought if I can get rid of it, it would be great. Especially, too, on Knickerbocker (Lake), I want to help do my best to keep the lake in good shape.”  

Gleason reached out to Rebecca Jacobs, natural resources program manager at Boothbay Region Water District, who confirmed the plant. Jacobs helps mitigate threats to the watershed, and she has a special interest in invasive plants. Native to Europe and Asia, purple loosestrife (Lythrum salicaria) is a poster child for invasive species; its long stem of pretty, brightly colored flowers masks the harm it can do once established outside its natural habitat.  

"It's beautiful. But it did not come with its natural predators,” she said. “No diseases, no viruses, no insects, no mammals or birds that feed off of it, or keep its population in check, which is what invasive plants are, essentially. It’s a plant that has no check and balance.”

While there are patches in Boothbay, it’s more prominent in Massachusetts and southern Maine, where it thrives in wet environments; Jacobs said it can become so prolific, it changes the ecology of an area, outcompeting native species, overrunning wetlands, ponds, roadside ditches and other water-rich habitats.    

It can also spread widely: Jacobs said one plant can produce up to 2.5 million seeds, which can remain viable for several years, even after traveling several days in water.   

“It's going to choke out the native vegetation in favor of itself. They're bullies, essentially,” Jacobs said. “All the voids will be occupied by the seeds and new plants, new seedlings of this plant. So, what we see as a pretty dynamic, diverse landscape along this shoreline would be a monoculture over time.” 

It can also impact both terrestrial and aquatic environments: Jacobs said too much can degrade fish habitats, change local hydrology and block shorelines; and, as it moves into a water body, it can also alter the littoral zone, a critical nearshore habitat where fish, amphibians and other wildlife spawn.   

Jacobs has seen purple loosestrife on Knickerbocker Pond, Adams Pond, along Back River and other areas in small to moderate quantities. She tries to mitigate it as she can, enlisting the help of homeowners, because it's best dealt with sooner rather than later.  

“From somebody who has seen it completely absorb a wetland or water body more than 20 years ago and completely change the hydrology, it would be a multi-million-dollar problem. This particular species here on this peninsula ... we're capable of managing it by hand,” she said.   

So what should someone do? The first step is to identify it. According to Maine Department of Agriculture, Conservation and Forestry (DACF), purple loosestrife’s flowers are half an inch to three-quarters of an inch wide, in long, crowded spikes with five to seven petals. At first glance, it may look like native fireweed or blue vervain. However, fireweed flowers are larger (around one inch) and four-petaled, and blue vervain leaves are toothed with very small five-petaled flowers less than a third of an inch.   

“As soon as it's blooming, as soon as you're positive of its identification, that's when you want to eradicate it. You want to make sure that you can eliminate it before going to seed,” Jacobs said, clarifying that it blooms in late July through early September. "... Doing nothing essentially is giving in to the plant and allowing the infestation to occur."

Once identified, purple loosestrife can be removed at several levels. The easiest, but moderately effective, is to cut the plant at its stem and keep it in a vegetative state. However, more established plants have a woody root system that may require digging and full removal. Maine DACF says persistent cutting or pulling multiple times during the growing season may kill the plant but the agency recommends doing it at least three times a year for three years. Herbicides may also be effective but are not appropriate for the Boothbay region because many of the plants are on or adjacent to sensitive public water sources. For any method, it is recommended to bag the flower heads to prohibit the spread of seeds.   

“We're all stewarding some patch of land, whether we rent, whether we own, whether we live in an urban or a rural environment,” Jacobs said. “Why not take five minutes to cut their heads off every year and keep them from continuing to spread and causing more problems?”  

For more information on purple loosestrife, see this pamphlet from Maine DACF: https://www.maine.gov/dacf/mnap/publications/loosestrife.pdf  

For help identifying possible purple loosestrife, email a close-upphoto that includes the plant leaf and flowers to Jacobs at rjacobs@bbrwd.org