Coming down the water, with a wide-open mouth of vibrating teeth, the milfoil harvester is a light blue paddle-wheeled contraption worthy of a Dr. Seuss rhyme. Or maybe it’s something Jules Verne would have moored at his lake cabin.
The combine-like machine is a common sight on Twin Cities lakes, ever since the early 1990s when the Eurasian water milfoil infestation really took off. The weed crowds out native plants, which in turn hurts the fish populations that feed on those plants. Mostly, though, it was the outcry from a repelled public that spurred local anti-milfoil efforts. Milfoil is a nuisance to boaters and anglers, and a possible hazard to swimmers, who get tangled up in its creepy tendrils. And it grows like crazy—up to a foot a week. This year seems particularly bad, and there are several theories why. For example, the lack of snow last winter may have allowed more light to reach the plants beneath the lake ice, extending the growing season.
In Minneapolis, between Memorial Day and Labor Day a crew with two harvesters and two trucks rotate between city lakes. They remove 20 tons of weeds each day, focusing on priority sites like swimming areas. Where does it all end up? At a compost site at Fort Snelling State Park. The machines, which are made in Wisconsin, are on the lakes for 6-10 hours each day, six days a week. They make multiple passes over the same areas because the paddle wheels blow down the weeds as the harvester approaches, but then the weeds straighten back up. “It’s like trying to mow your lawn blindfolded,” one driver told me.
On a sunny morning a few days later, crewmember Tom Tollefson took The Rake for a ride on Cedar Lake. Tom allowed me to sit briefly at the controls, and I couldn’t resist gunning it. The harvesters are surprisingly fast. Tollefson took over and dropped the front shovel into the water. The blades on the business end of the shovel are like a giant hair clipper, and they cut the weeds off 3 to 4 feet below the surface. Then a series of conveyor belts ratchet the weeds up the shovel and to the back of the boat. The milfoil comes out of the water in tangled mats, and it smells faintly of fish and chlorine. No one has found a good use for harvested milfoil. Several years ago, a curious park employee tried to get a neighbor—a farmer—to feed the weed to his cows. But the man showed him a watering pond that had already been infested with milfoil. Even with their wide-ranging herbivorous appetite and two stomachs, the cows fastidiously avoided it.
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