HOFFMAN, Minn. -- If you drove past Elk Lake in Hoffman this summer, you may have seen an unusual sight: A mechanical harvester out on the water, baling up weeds.

"It’s a big barge that floats with a cutter bar and a conveyer belt, like an underwater combine," said operator Troy Friedrich, co-owner of Ottertail-based Aquatic Weed Harvesting.

This the first time Hoffman, a city about 25 miles west of Alexandria, has hired a mechanical harvester for its lakeshore, and it's not alone in struggling with a bumper crop of lake weeds this summer. Throughout the Alexandria lakes area, as well as the state, lakeshore owners and local government bodies have been contending with an abundance of aquatic weeds. A warm spring, low lake levels and the effects of zebra mussels created conditions where aquatic plants thrived, to the consternation of swimmers and boaters.

So far in 2021, the Minnesota DNR has issued 6,135 Aquatic Plant Management permits, the most since at least 2010, according to Shane McBride, DNR aquatic plant management program coordinator. Throughout the 2010s, the number of permits has grown from about 3,500 in the beginning of the decade to around 6,000 by the end of the decade.

McBride attributes this year's increase to people returning to their seasonal properties, plant abundance amplified by low water levels, and a typical bump in permitting for weed rollers, which need to be renewed every three years.

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Zebra mussels have also been found in Elk Lake, and they are notorious for clarifying the water, allowing sunlight to penetrate and spur plant growth.

Friedrich said his business is booked every year, and this year was extra busy.

“I’ve had to turn away mountains of work, I’ll be honest," he said.

Curly-leaf pondweed has been unusually thick this year, he said, and chara, which covers the lake bottom like carpet, has also been bad. He blames lower water levels and higher water temperatures.

“Some of the lakes we’ve been cutting on are two feet lower than normal,” he said. “We’re seeing water temperatures at 80 degrees plus.”

Typically, lake water temperature is in the low- to mid-70s, he said.

“The other thing that contributes to the weeds too is a lot of runoff," he said. "You look at all these homes around these lakes, they’re all fertilizing their lawns. Well, that fertilizer needs somewhere to go, and it runs into the lake.”

Hoffman city workers found themselves stunned by the weed growth on Elk Lake.

"It was just overtaking everything," said Tina McGrath, who manages the city's campground. “The weeds have never been this bad.”

Hoffman, with a population of 681, lies about 22 miles west of Alexandria. Its businesses depend on the traffic generated by visitors to the lake.

It's so important that the city of Hoffman, the Grant County Lions and the Hoffman Lion's Club teamed up to pay several thousand dollars for the mechanical harvester. Friedrich cleared weeds along 400 feet of shoreline, and 75 feet out, going down five feet.

“Elk Lake is very, very important to the community and we do not want that lake to be not good," said Muriel Krusemark, economic developer for Hoffman. "There are lots of people who come to Elk Lake. It’s a spring-fed lake and it’s never been green, really, and this year it was mostly weeds.”

“The lake is one of the main attractions here in Hoffman," said City Clerk Janee Strunk. "It’s why many people come to town.”

The city has funded an herbicide in previous years, but it seemed to be overwhelmed by the number of weeds this year, Strunk said. She expects there to be an ongoing battle with the weeds, but was happy with the result of the mechanical harvesting.

“We picked right back up as soon as the weeds were gone," she said. "The kids were right back in there.”