Invasive milfoil threatens Maine lakeside property values and recreation


Colin Holme watched a little girl walk a few feet into Lake Arrowhead earlier this year and was startled to see invasive yarrow enveloping her.

“It was horrible,” said Holme, executive director of the Lakes Environmental Association in Bridgton, which monitors 41 lakes and ponds in southwest Maine for invasive aquatic plants and water quality. “I remember swimming in lakes when I was young and how much I didn’t like swimming through the plants.”

The invasive plants, believed to have originated in the southern states, first appeared in Maine in 2003. Although the weed is not known to harm humans, it spreads quickly and is spread from infested lakes to others, mostly through uncleaned boats.

Yarrow is now found in 32 Maine lakes, four more than before the COVID-19 pandemic, as more people sought outdoor activities like boating and stayed longer on lakes into the fall. Aside from being an eyesore and uncomfortable for swimming and boating, widespread yarrow infestation can be costly for homeowners by lowering lakeside property values, studies have found.

According to the Maine Department of Environmental Protection, homeowners in Maine’s southern five counties could see home depreciation in excess of $11 million. The cost of controlling invasive species, including yarrow, could eventually reach $4 million a year, it said. This number does not include losses from tourism, fishing and water sports.

Some areas of Maine are already affected. In 2007, homeowners in Limerick, which borders Lake Arrowhead, successfully petitioned the city to lower their home valuations by 10 to 20 percent because of yarrow in the lake. The artificial lake was constantly infested with yarrow, partly because it is comparatively shallow, allowing sunlight to reach its bottom and help the plants grow.

Maine is home to two invasive species of yarrow that grow rapidly, robbing other plants of their habitat and making life in the lake difficult for fish and birds. These include the legendary Maine loons, who need a quarter mile to land and clear water to see their prey in the lake.

Alternate yarrow in the Northwest River Bay of Sebago Lake in Cumberland County. Yarrow looks like a raccoon’s tail when fanned out in water and is odorless unless sitting in stagnant water. Photo credit: Courtesy of the Lakes Environmental Association

The most common species of yarrow in Maine is the variable leaf yarrow, which is odorless and bushy in appearance like a raccoon’s tail in water. It grows in shallower waters towards the lake shore and blooms above the lake surface. It can grow 15 feet long. Yarrow is also found in some lakes and is difficult to eradicate. Both usually grow from May to October.

Yarrow is found from southernmost Maine to Washington County, usually in lakes and rivers that are easily accessible from the Interstate 95 corridor. All New England states, 41 other US states and six Canadian provinces are controlling yarrow and other invasive plants.

Holme anticipates that yarrow will continue to spread throughout Maine. The COVID-19 pandemic brought more motorized boats to the lakes as consumers looked home for outdoor activities, and this increased activity has continued well into the fall. The motorized boats cut up the yarrow and helped it spread, Holme said.

Clearing lakes of yarrow is a labor-intensive and ongoing process, mostly undertaken by about a dozen nonprofit groups that aren’t well-funded despite the relatively low cost of killing the plants, Holme said. About a quarter of the Lakes Environmental Association’s funding comes from the Department of Environmental Protection, which gets its money mostly from the stickers that boat owners are required to buy and from grants.

The sticker program was passed by the legislature in 2002 and is funded by fees for motorized watercraft operating on inland waterways, which are higher for foreign registrants. The environmental association also receives money from cities, lakefront homeowners and private donations.

The largest pot of money comes from a private foundation with a board member interested in yarrow. It donated $100,000 in each of the first two years and $75,000 in the last two years. The board member lives in Massachusetts, where nearly 10 percent of the state’s 3,000 lakes are polluted.

“He realized how bad yarrow is in Massachusetts and thought we had a chance to fight it back in Maine,” Holme said.

The rest of the funding comes from recruiting local landowners on lakes like Long Lake, which is surrounded by the cities of Naples, Bridgton and Harrison. But only 16 percent of homeowners contribute, he said. The cities’ money is also sparse. Naples, which has the most lakefront properties, donates $10,000 annually to the nonprofit, Bridgeton $1,500 and Harrison has not yet contributed.

The association requires about $200,000 a year for control measures and the same for the cleanup. Holme worries about what will happen when funding from the non-government foundation ends.

“Once the funding is gone, the yarrow will come back,” he said.

Harvesting yarrow in Sebago Cove. Photo credit: Courtesy of the Lakes Environmental Association

Prevention is a big part of what the association focuses on, trying to get boat owners to clean their boats before and after using them in a lake. This can be a hose down, wiping with a towel, or visually inspecting all parts of the boat to see that there are no yarrow plant fragments stuck anywhere.

A simple way to think about cleaning is to “clean, drain and dry” before and after each visit to the lake, said John McPhedran, a biologist in the Department of Environmental Protection’s Invasive Aquatic Species Program. Cleaning should be done in such a way that no used water gets into the lake.

He said early detection is key to keeping yarrow at bay. In 2020, the state inspected more than 100,000 boats, most of them free of invasive aquatic plants. A constant challenge is thinking of ways to reduce the risk of human spread, especially with more people boating later in the fall. Animals spread yarrow, but not to the same extent as boaters, he said.

Large traps are used to contain yarrow in Sebago Lake.Benthic barriers are large tarps placed over a yarrow flower to kill it off in winter, as seen here at Sebago Cove. Photo credit: Courtesy of the Lakes Environmental Association

To rid an infected lake of yarrow, the Lakes Environmental Association doesn’t use chemicals but has three methods. Divers pull up the yarrow roots and feed the plant through a suction hose, which dumps it onto the deck of a boat for disposal. In large areas with very few plants, divers hand pull and bag the plants. In large areas where only one species of yarrow occurs, it creates tarpaulin barriers that suffocate the plants over the winter.

“The long-term prognosis is that unless we give more money, more education and more recognition to the problem, it’s only going to get worse,” Holme said. “At some point we will be overwhelmed.”