Tracking invasive plant species in Adirondack waters

Trained in the art of identifying watermilfoil and pondweed, one woman prepares to defend her favorite lakes, ponds, and beaches

By Jill U. Adams

Eurasian watermilfoil. Photo credit Robert L. Johnson, Cornell University,

In an old motel on the shore of New York’s Lake George, nineteen people crowd around some twenty plant specimens set out on long tables. Married couples, a group of older men, a young mother, and a handful of students, we wear flannel and fleece, rip-stop nylon and baseball caps to the Adirondack Park Invasive Plant Program training session for volunteers. The defunct motel now houses the Darrin Fresh Water Institute, and we are here to learn to survey lakes and ponds for aquatic plants that don’t belong.

Devious in both habit and disguise, invasive aquatic plants like Eurasian watermilfoil, curly-leaf pondweed, and water chestnut threaten the 30,000 miles of rivers and the 3,000 ponds and lakes of the Adirondack Park. With tiny toeholds, these foreign invaders take root and proliferate, free of the environmental checks and balances of their homelands. Because they out-compete their native peers, such plants reduce fish spawning sites and interfere with recreational activities like swimming, fishing, and boating.  

No one, state agencies or Adirondack municipalities, wants to spend money preventing something that "might" be a problem. And yet, once an infestation takes place, it’s too late to eradicate, says program coordinator Hilary Oles. Monitoring by volunteers is the cornerstone of the Adirondack Park Invasive Plant Program, now in its tenth year. 

I was ready to battle water-logged weeds in my beloved Adirondack places: the remote lake reachable only by hiking through the woods, my family’s favorite public beach, and our own cabin’s pond, encircled with water lilies. However, I didn’t know what a challenge it would be. The first tricky part was distinguishing the invasive species from their look-alike native cousins. The second would be gathering submerged plants from murky pond bottoms. 

Standing at the table, I had a hard time telling the bad plants apart from the good without peeking at their labels. Encouraged to touch, I soon learn that pulling the plants out of their water-filled tubs makes it harder to see the shape of the leaves or how they’re attached to their stems.  Better to move them under water where the feathery leaflets float obligingly into formation. 

When I study them side-by-side, I could make out the difference between the evil Eurasian watermilfoil and the angelic bladderwort.  Much harder was distinguishing the foreign species from the five (!) native watermilfoils.  The stems of the invader are slightly pinker, but the whorled arrangement of the leaves, like the blades of a fan, is the same as that of common watermilfoil. As I contemplate repeating this task with unlabeled plants alone in my canoe, I begin to fret. I’m relieved when we’re instructed to collect and mail suspicious samples to Oles for confirmation.

The pondweeds were easier. Like seaweed, the leaves of the three native species on display had softly rippled edges, whereas those of curlyleaf pondweed were more tightly frilled like lasagna noodles.

Nearly 100 people, both residents and summer folk, will keep watch over the park’s waterways for signs of infestation this year. Oles is training us today, but she knows her pupils are as knowledgeable about their piece of the park as anyone. Volunteers want to protect the pristine waterways, she says. “They feel that by keeping a watchful eye on them that they can help be a part of that protection.”

Patricia Goldberg is a new recruit who wants to survey Fourth Lake, where she has spent summers since 1946.  Now a year-round resident, she’s aware of the problem of invasives in the more popular Lake Luzerne, downstream from her lake. Trainee Elsie Tai is particularly pleased to have a volunteer opportunity that ties together so many interests: her environmental science degree, her favorite lake, and her family. She lives in the Adirondacks and spends lazy summer days with her husband and three-year old daughter at Chatiemac Lake. “We’ll make it part of our family outings,” she says.  “It will be an educational tool for my daughter.”

After lunch, Oles digs through a bin of visual props: shoreline maps and survey sheets, a plant identification guide, a plastic food bin with which to examine samples in water, and Ziplocs to collect specimens. The only specialized instrument is a throw rake for collecting out-of-reach plants.  We can make our own by cutting off the handle of an ordinary garden rake and attaching a long nylon cord. Launching it from a boat, the rake end sinks to the lake bottom. Dragging it slowly back in by the chord, plant species are snagged along the way. 

We left the motel and tromped down to the dock to learn how to conduct a survey. Larry Eichler, a scientist at the Institute, uses a throw rake to pull in submerged plants. Still trainees, we made our best guesses.  In addition to identifying the presence of any invasive plants, we are to record where they are growing, how many, how deep, how dense, and if they cohabitate with other species.  “It helps to know the length of your boat,” says Oles, who measures large plant beds with her 12-foot kayak. 

Two weeks later, it’s the Fourth of July and I’m in my canoe gazing into the green-black shallows of our pond. It still seems daunting, searching for the first squatter hiding underwater. I see a native pondweed (no lasagna edges) in bloom—yay! But I also see the colorless remnants of old milfoil.  When I pull up a sample, it seems bushier than the evil Eurasian.  But I’ll know where to look for fresh growth later in the month –mid-July to mid-September is the best time to survey. And if I’m not sure, I’ll being mailing a slime-filled Ziploc to Oles.

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