Purple Loosestrife
Invasive SpeciesFound in 278 lakes
Purple Loosestrife appears on state infested-waters lists for 278 surface waters. Boaters and anglers moving gear in or out of those lakes carry a clean-drain-dry obligation under state law. At 278 infested lakes, Purple Loosestrife is past the "containable" stage in the upper Midwest — every public boat-launch on uninfested water should now assume incoming boaters may be carrying it.
The presence of Purple Loosestrife 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 Purple Loosestrife
| Lake | County | State | Grade | Depth |
|---|---|---|---|---|
| White Sand Lake Deep | Vilas | WI | A | 63 ft |
| Little Spider Lake | Vilas | WI | A | 23 ft |
| Long Lake | Bayfield | WI | A | 28 ft |
| Long Lake | Burnett | WI | A | 41 ft |
| North Twin Lake | Polk | WI | A | 27 ft |
| Stone Lake | Washburn | WI | A | 49 ft |
| Shell Lake | Washburn | WI | A | 36 ft |
| Rinehart Lake | Portage | WI | A | 27 ft |
| Paddock Lake | Kenosha | WI | A | 32 ft |
| Hasbrook Lake | Oneida | WI | A | 50 ft |
| Lower Eau Claire Lake | Bayfield | WI | A | 41 ft |
| Tozer Lake | Washburn | WI | A | 53 ft |
| Osprey Lake | Sawyer | WI | A | 32 ft |
| Dutch Hollow Lake | Sauk | WI | A | 38 ft |
| Buffalo Lake | Oneida | WI | A | 27 ft |
| White Sand Lake | Vilas | WI | A | 63 ft |
| Lower Sugarbush Lake Deep | Vilas | WI | A | 61 ft |
| Mercer Lake | Oneida | WI | A | 23 ft |
| Des Moines Lake | Burnett | WI | A | 37 ft |
| Sand Lake | Burnett | WI | A | 73 ft |
| Middle Mckenzie Lake | Burnett | WI | A | 45 ft |
| Buskey Bay Lake | Bayfield | WI | A | 51 ft |
| Hodstradt Lake | Oneida | WI | A | 36 ft |
| Flambeau Lake | Vilas | WI | A | 78 ft |
| Mosslake_deep | Vilas | WI | A | 29 ft |
| Moss Lake East | Vilas | WI | A | 29 ft |
| Lake Beulah | Walworth | WI | A | 58 ft |
| Okauchee Lake | Waukesha | WI | A | 90 ft |
| Powers Lake | Kenosha | WI | A | 33 ft |
| Silver Lake | Waukesha | WI | A | 40 ft |
| Silver Lake | Vilas | WI | A | 19 ft |
| Mirror Lake | Waupaca | WI | A | 43 ft |
| Kusel Lake | Waushara | WI | A | 29 ft |
| Ottawa Lake | Waukesha | WI | A | 16 ft |
| Spider Lake | Vilas | WI | A | 43 ft |
| Crooked Lake | Oconto | WI | A | 37 ft |
| Beaver Dam Lake | Barron | WI | A | 106 ft |
| Ashippun Lake | Waukesha | WI | A | 35 ft |
| Bear Lake | Waupaca | WI | A | 62 ft |
| Long Lake | Waupaca | WI | A | 76 ft |
| Long Lake | Waushara | WI | A | 71 ft |
| Rock Lake | Kenosha | WI | A | 33 ft |
| North Lake | Waupaca | WI | A | 33 ft |
| Shadow Lake | Waupaca | WI | A | 41 ft |
| High Lake | Vilas | WI | A | 36 ft |
| Red Cedar Lake | Barron | WI | A | 53 ft |
| Big Sand Lake | Burnett | WI | A | 55 ft |
| Lake Emily | Portage | WI | A | 35 ft |
| Lower Eau Claire Lake | Bayfield | WI | A | 41 ft |
| Gilbert Lake | Waushara | WI | A | 65 ft |
Showing 50 of 278 infested lakes.
Frequently Asked Questions
How many lakes have purple loosestrife?
Purple Loosestrife has been documented in 278 graded lakes: 278 in Wisconsin.
Does purple loosestrife affect water quality?
Invasive species can significantly affect lake ecosystems. They may alter nutrient cycling, displace native species, and change water clarity. Lakes with purple loosestrife should be monitored for changes in water quality over time.
Invasives Found With Purple Loosestrife
Co-occurs in 173 lakes · 432 total
Co-occurs in 146 lakes · 493 total
Co-occurs in 106 lakes · 363 total
Co-occurs in 84 lakes · 244 total
Co-occurs in 81 lakes · 688 total
Co-occurs in 22 lakes · 99 total
Source: EPA National Aquatic Resource Surveys, 2026.