Plainfield Tunnel Channel Lakes

State Natural Area (No. 226)

Location: Waushara County. T20N-R9E, Sections 17, 18. 97 acres.

Access: From the intersection of State Highway 73 and County Highway BB on the east side of Plainfield, go east and south on 73 0.85 mile to a parking area west of the road.

Description: The Plainfield Tunnel Channel Lakes provide specialized habitat for one of our rarest plants, Fassett’s locoweed (Oxytropis campestris var.chartacea). This federally threatened member of the bean family with magenta flowers and silvery-green leaves is endemic to Wisconsin – it grows here and nowhere else. Named after University of Wisconsin botanist Norman Fassett who first described the species, it only occurs on the fluctuating shorelines of lakes in the Central Sands area of Wisconsin. It is adapted to the sandy shores of shallow seepage lakes whose shorelines fluctuate widely over months or years depending on rainfall and drought patterns. When the shore is exposed, locoweed seeds in the seed bank germinate, grow, flower, and drop seeds. The plant requires open, sunny habitat and relies on periodic flooding to kill shade-producing trees that invade the shoreline in dry years. Locoweed survives inundation - up to years at a time - by persisting in the lake bottom's seed bank until the water levels drop. Protected are the shorelines of three lakes in a string of 13 lakes and ponds lying in a "tunnel channel" created by a meltwater river flowing beneath the glacial ice. The lake basins were created from buried blocks of ice left behind when the tunnel collapsed. Why Fassett's locoweed is endemic to Central Wisconsin is unknown but it may be related to the effects of the glacial lake, which once covered the area 10,000 years ago. While shading and competition by trees and other plants are the primary natural threats, trampling by humans and disturbance from off-road vehicles pose far more serious threats to these sensitive plants. Plainfield Tunnel Channel Lakes are owned by the DNR and were designated a State Natural Area in 1990.