Purple Loosestrife: 242 Lakes with Records

Purple Loosestrife appears on state infested-waters lists for 242 surface waters. Boaters and anglers moving gear in or out of those lakes carry a clean-drain-dry obligation under state law. At 242 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 change a lake's clarity, phosphorus or algae readings, which measure the water itself, not the species living in it. Invasive presence is still worth reading alongside those numbers.

242

Lakes with records

242

Wisconsin

Lakes with Purple Loosestrife

Lake	County	State	Depth
Green Lake	Green Lake	WI	236 ft
Lake Beulah	Walworth	WI	58 ft
Powers Lake	Kenosha	WI	33 ft
Big Sand Lake	Burnett	WI	55 ft
Osprey Lake	Sawyer	WI	32 ft
Gaslyn Lake	Burnett	WI	12 ft
Wind Lake	Polk	WI	7 ft
Boulder Lake	Vilas	WI	23 ft
Spider Lake	Vilas	WI	43 ft
Pickerel Lake	Oconto	WI	10 ft
Beaver Dam Lake	Barron	WI	106 ft
Silver Lake	Kenosha	WI	44 ft
Silver Lake	Waukesha	WI	40 ft
Silver Lake	Vilas	WI	19 ft
Mirror Lake	Waupaca	WI	43 ft
Ashippun Lake	Waukesha	WI	35 ft
Kusel Lake	Waushara	WI	29 ft
Spencer Lake	Waupaca	WI	53 ft
Little Spider Lake	Vilas	WI	23 ft
Bone Lake	Polk	WI	43 ft
Ottawa Lake	Waukesha	WI	16 ft
Bear Lake	Oneida	WI	20 ft
Bear Lake	Barron	WI	87 ft
Bear Lake	Waupaca	WI	62 ft
Long Lake	Waupaca	WI	76 ft
Long Lake	Bayfield	WI	28 ft
Long Lake	Burnett	WI	41 ft
Long Lake	Fond du Lac	WI	47 ft
Long Lake	Waushara	WI	71 ft
Crooked Lake	Oconto	WI	37 ft
Rush Lake	Winnebago	WI	5 ft
Rock Lake	Kenosha	WI	33 ft
North Lake	Waupaca	WI	33 ft
Red Cedar Lake	Barron	WI	53 ft
Red Cedar Lake	Jefferson	WI	6 ft
Lake Galilee	Ashland	WI	23 ft
Pewaukee Lake	Waukesha	WI	45 ft
Shadow Lake	Waupaca	WI	41 ft
High Lake	Vilas	WI	36 ft
Camelot Lake	Adams	WI	24 ft
Stone Lake	Washburn	WI	49 ft
Island Lake	Rusk	WI	54 ft
Island Lake	Oneida	WI	26 ft
North Twin Lake	Polk	WI	27 ft
Lake Emily	Portage	WI	35 ft
Big Lake	Polk	WI	24 ft
Reisner Lake	Florence	WI	5 ft
Kentuck Lake	Vilas	WI	40 ft
Lower Eau Claire Lake	Bayfield	WI	41 ft
Lac la Belle Lake	Waukesha	WI	45 ft

Showing 50 of 242 lakes with a record.

Frequently Asked Questions

How many lakes have purple loosestrife?

Purple Loosestrife is recorded in 242 measured lakes: 242 in Wisconsin. 242 of them carry a state infested-waters listing or an established population.

Does purple loosestrife affect water quality?

An established invasive population can change how a lake works — altering nutrient cycling, displacing native species, and shifting water clarity. Clarity is the one to watch: filter-feeders can make water read clearer on a Secchi disk without any drop in nutrient loading, so a lake with purple loosestrife is worth reading alongside its clarity number rather than through it.

Invasives Found With Purple Loosestrife

Curly-Leaf Pondweed

Co-occurs in 145 lakes · 387 total

Chinese Mystery Snail

Co-occurs in 133 lakes · 469 total

Banded Mystery Snail

Co-occurs in 95 lakes · 341 total

Rusty Crayfish

Co-occurs in 78 lakes · 233 total

Zebra Mussel

Co-occurs in 59 lakes · 609 total

Starry Stonewort

Co-occurs in 17 lakes · 79 total

More on invasive species and lake health

Zebra Mussel Spread: How Many Lakes Are Affected?

Zebra mussel counts from the lakes LakeQuality tracks, the counties that show up most often, and the Clean, Drain, Dry rules that still matter.

Lake Water Quality Explained: What the Readings Mean

How nutrient and algae readings are read against EPA ecoregion condition classes, what each class means in the water, and why a clean reading is not a clearance.

What to Check Before Buying Lakefront Property

Before you buy lakefront, check the water: clarity trend, nutrient impairment, algae advisories, invasive species, and depth — a data-backed checklist.

Source: EPA National Aquatic Resource Surveys, 2026.