Japanese Knotweed
Invasive SpeciesFound in 17 lakes
Japanese Knotweed appears on the {{stateName}} infested-waters lists for 17 surface waters. Boaters and anglers moving gear in or out of those lakes carry a clean-drain-dry obligation under state law. 17 lakes — narrow enough that aggressive containment is still on the table. Most upper-Midwest invasives that established here did so quietly over a decade before anyone noticed, so a low number today is not a guarantee for tomorrow.
The presence of Japanese Knotweed does not directly change a lake's LakeGrade rubric score — the grade measures the water itself, not the species inhabiting it. But invasive presence is a meaningful adjacent signal worth reading alongside the grade.
Lakes with Japanese Knotweed
| Lake | County | State | Grade | Depth |
|---|---|---|---|---|
| Long Lake | Bayfield | WI | A | 28 ft |
| Deer Lake | Polk | WI | A | 46 ft |
| Lake Nebagamon | Douglas | WI | A | 56 ft |
| Tabor Lake | Burnett | WI | A | 28 ft |
| Swan Lake | Columbia | WI | A | 82 ft |
| Springville Pond | Portage | WI | A | - |
| Yellow Lake | Burnett | WI | A | 31 ft |
| Big Roche A Cri Lake | Adams | WI | A | 20 ft |
| Balsam Lake | Polk | WI | A | 37 ft |
| Mcdill Pond | Portage | WI | B | 19 ft |
| Wapogasset Lake | Polk | WI | B | 32 ft |
| Balsam Lake Little Balsam Site | Polk | WI | B | 37 ft |
| Alpine Lake | Waushara | WI | B | 18 ft |
| Amherst Millpond | Portage | WI | C | 7 ft |
| Cedar Lake | Polk | WI | C | 32 ft |
| Tainter Lake | Dunn | WI | C | 37 ft |
| Mason Lake | Adams | WI | D | 9 ft |
Frequently Asked Questions
How many lakes have japanese knotweed?
Japanese Knotweed has been documented in 17 lakes, 0 in Minnesota and 17 in Wisconsin.
Does japanese knotweed affect water quality?
Invasive species can significantly affect lake ecosystems. They may alter nutrient cycling, displace native species, and change water clarity. Lakes with japanese knotweed should be monitored for changes in water quality over time.
Source: EPA National Aquatic Resource Surveys, 2026.