The Clearwater Valley in the midst of a waterlily invasion

A field of green greets both residents and visitors to many of the lakes in the Clearwater Valley. However, this is not the field of green you may be thinking of – This particular landscape lacks barbecue pits, lawn furniture and a kayak propped up against an old ponderosa pine. The field of green to which I'm referring is the blanket of waterlilies that now cover many acres of shorefront. While native waterlilies still exist in the Clearwater, the native species are being pushed out as invasive fragrant waterlilies colonize at an increasing voracious rate.

Invasive fragrant waterlilies first appeared in the Clearwater Valley as early as the 1930s. It is highly likely that the lily was transported and planted by the former owners of the Legendary Lodge on Salmon Lake. Over the last several decades, the plant has spread greatly and prolific populations of these lilies can now be found in Salmon, Placid, Seeley, Inez and Alva, among others.

In the face of catastrophic wildfires, extreme drought and a COVID-19 resurgence why should we worry about a bunch of waterlilies, that on the surface seem innocuous?

First, invasive lilies can dramatically reduce habitat and spawning areas for native fish, giving predaceous, nonnative fish an undue advantage.

Second, these invasive plants contribute to increased algal growth and sedimentation rates, both of which can diminish water quality over time.

Thirdly, invasive lilies impede, and in some cases completely restrict, our use and enjoyment of our lakes. Boating and swimming are impacted by dense lily stands, and mosquito habitat is dramatically increased making outdoor activities in the early summer less pleasurable. For some lakeshore residents, docks can no longer be accessed and pipes that used to draw water from the lake are no longer operational due to dense mats of lilies and associated sediment loads.

But what can we do about it? Many residents have battled lilies for years with little success. However, in 2020, CRC took a new approach by introducing the Make-the-Cut program. Working with volunteers, CRC clipped invasive lilies at Placid and Salmon Lakes. In 2021, CRC included Seeley Lake in the Make-the-Cut effort, and set up a demo site on Seeley Lake, introducing a program of clipping and digging.

Frustrated residents have asked, "Will this really work?" The answer is not simple.

Yes, it will work, but only if consistently undertaken over a long period of time. And if the majority of landowners on a given lake fail to participate, removal efforts will be needed indefinitely in order to maintain any gains made. It took decades for the invasive lilies to colonize vast shoreline areas and it will likely take decades to remove them, assuming that community-wide efforts are initiated to stop their spread.

The program CRC has introduced includes a combination of clipping and digging. We do not use rakes as they often serve to spread the lilies, nor do we use herbicides to due potential environmental and other unanticipated side effects. Optimally, the clipping needs to take place at least twice annually, once shortly after initial leafing (to reduce plant to photosynthesis) and then after the plants have flowered.

We also dig out the roots/rhizomes of the lilies to address the source population. Removing the rhizomes can be highly effective, but it is difficult work, and the benefits of both cutting and digging will be negated if maintenance efforts cease.

In the early summer of 2022, we also plan to install bottom barriers at our demo site on Seeley Lake to determine their efficacy from a management perspective. Bottom barriers will not be used to significantly reduce overall populations, as the rhizomes of the lilies will allow the plant to grow out from underneath the barriers. However, it is our hope that barriers can be used as an interim management tool to enable lakeshore residents to better access docks and other infrastructure.

Invasive lily removal is a daunting task. However, if we fail to act, lilies will continue to colonize lakeshore areas. At Holland Lake, the Forest Service has engaged in similar invasive lily reduction efforts over the past several years and have been successful in their initial reduction efforts. It is our hope that similar efforts can be undertaken on a broader scale in the Clearwater Valley. While we can't resolve this issue overnight, we can stem the tide and start down the path to reducing the population of invasive lilies.