Prized by 18th century traders, fragrant lily now choking Clearwater drainage

It’s believed that introduction of the fragrant water lily to the Pacific Northwest likely occurred around the 1890s and the Seattle World’s Fair. Since then, the plant has infested water bodies along the West Coast and is now widely spread across western Montana.

Citing its alarming spread and ability to crowd out native vegetation, Missoula County has declared the fragrant water lily as a noxious species, though eradicating it from western Montana may not be easy.

In fact, the results of an initial herbicide treatment conducted this summer won’t be known until later next year. What is certain, however, is that the lily has already infested large areas of the Clearwater River system, including water bodies around Seeley Lake.

It also has crossed the divide into the Swan River drainage.

“It showed up on Holland Lake five to 10 years ago,” said Beth Gardner, a fish biologist on the Flathead National Forest. “I’m absolutely alarmed by how aggressive this plant is. I have seen it out-compete some native vegetation and as a biologist, I’m concerned about this.”

Bryce Christian of the Missoula County Weed District said property owners along the Clearwater River system, along with frequent lake visitors, have grown concerned with the apparent spread of the invasive species.

The Flathead National Forest, also concerned, petitioned the county to list the fragrant water lily as a county noxious weed. With funding from the Montana Department of Natural Resources and Conservation, county researchers began to look into the plant, map its location and explore potential treatments.

“Our results won’t be available until a year after treatment. The herbicides take a little longer to do their work in the system,” said Christian. “We also put in water sampling points both above and below the infestations. We wanted to make sure we knew what the herbicide was doing in the system.”

The fragrant water lily is native to the East Coast. Prized for its ornamental flowers, it became an interest among horticulturists as early as the 1700s. The plant was traded to Europe later that century.

Christian said it’s believed that introduction of the plant to the Pacific Northwest likely occurred around the 1890s and the Seattle World’s Fair. Since then, the fragrant water lily has infested water bodies along the West Coast and is now widely spread across western Montana.

“Ours happened to show up on Salmon Lake at what’s now known as Legendary Lodge,” said Christian. “It was built by one of the copper baron sons. In the early 1900s, people associated with William Clark Jr. really liked this lily and planted it at the bay just below the lodge.”

When early Early botanists found the species, they confused it with other native lilies found in western Montana including Brasenio schreberi, or the water shield, and Nuphar polysepala, or the yellow pond lily.

But unlike the native species that grow sparse and intermix with native vegetation, the fragrant water lily grows thick, matting entire coves and choking out native plants. Biologists fear that could eventually upset the aquatic food chain if left unchecked.

“We found it fairly spread throughout the system and concentrated in areas where there are lake shore homes or cabins,” said Christian. “It was clear we were seeing it move in the system, downstream of existing populations or along shores where cabins have existed for a long time.”

An aerial Google map of Salmon Lake shows a growing patch of the fragrant water lily. It was planted in small amounts in the bay intentionally in the early 1900s but has since spread throughout the Clearwater River system.

Mapping conducted by the county weed district found the fragrant water lily in large amounts in Rainy Lake, Lake Inez, Seeley Lake, Placid Lake, Salmon Lake, Black Lake, Elbow Lake and Blanchard Lake.

Areal mapping from 1930 showed a small patch of the fragrant lily planted intentionally on Salmon Lake near the historic Clark lodge. The plant now occupies the entire bay and has drifted to other locations of the lake where it’s beginning to take hold.

In Seeley Lake, the lily now covers 72 acres with the largest single cluster covering 19 acres. On Placid Lake, the plant occupies 15 acres with the largest single patch being more than 5 acres. It currently covers nearly half of Black Lake.

“We’re beginning to see a significant monoculture grow to the point where it’s almost choking out the water flow and some of the ways water is flowing through the system,” Christian said. “Competition for the fragrant water lily is out-competing native species.”

With mapping complete and herbicide testing underway in several specific locations, the county weed district and other biologists, including a plant geneticist from Sydney, Australia, will continue to monitor the system.

Doing so will reveal how effective the herbicide is and help biologists understand how long it takes to eradicate the plant and if it has any impacts on native species. Even then, Christian said, it will take time to rid the plant from western Montana’s prized mountain lakes.

“I think it’s going to be water body by water body,” he said. “There are good control options, but in some of those areas, there’s a solid mix of native vegetation and the fragrant lily. In areas where we have monocultures of the fragrant lily, that’s our best shot at eradicating it from the system.”