Butler Lake Flynn's Spring

State Natural Area (No. 257)

Location: Sheboygan County. T14N-R20E, Section 20. 158 acres.

Access: From the intersection of State Highway 67 and County Highway F in Dundee, go east on F one mile, then north on Division Road 1 mile, then east on Butler Lake Road 1.1 mile, then south on an access road 0.1 mile to a parking area, boat launch, and trailhead for the Butler Lake Trail. The wetlands are best accessed by canoe.

Description: Butler Lake and Flynn's Spring features a seven-acre shallow hard-bottom lake surrounded by sedge meadow. Previously, the site contained a tamarack hardwood swamp but a few years of high water levels has killed off most of the trees. Although the groundlayer has also been flooded, the aquatic vegetation and geologic features are still intact. Nearby Flynn's Spring is a small, spring brook flowing into the south end of Butler Lake. Chara covers the marl-bottomed Butler Lake while the dominant submerged aquatic species is Illinois pondweed. Emergents include white water-lily, bull-head pond-lily, and hard-stem bulrush. A small zone of sedges and bulrushes on the north end is the only open wetland. Older tamaracks, which formerly surrounded the lake, have died but the species is reproducing well along the northwestern and southern shores. Adjacent to the lake is Parnell Esker, a geologic feature known worldwide and used extensively for education. The esker is 5 to 35 feet in height and runs northeast southwest for about four miles. Of particular interest at this site is the presence two rare species-- the unicorn clubtail dragonfly (Arigomphus villosipes), and the swamp spreadwing (Lestes vigilax). Butler Lake and Flynn's Spring is owned by the DNR and was designated in 1992.