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Wisconsin State Natural Areas Program Plainfield Tunnel Channel Lakes (No. 226)

Fassett's Locoweed

Photo by Darcy Kind



Waushara County. T20N-R9E, Sections 16, 17, 18, 21. 192 acres.



The Plainfield Tunnel Channel Lakes provide specialized habitat for one of a rare member of the bean family which grows here and nowhere else. 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, 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. The plant 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 the rare plant 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.


Driving directions

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.


Plainfield Tunnel Channel Lakes is owned by:

  • WDNR


The DNR's state natural areas program is comprised of lands owned by the state, private conservation organizations, municipalities, other governmental agencies, educational institutions and private individuals. While the majority of SNAs are open to the public, access may vary according to individual ownership policies. Public use restrictions may apply due to public safety, or to protect endangered or threatened species or unique natural features. Lands may be temporarily closed due to specific management activities. Users are encouraged to contact the landowner for more specific details.

The data shown on these maps have been obtained from various sources, and are of varying age, reliability, and resolution. The data may contain errors or omissions and should not be interpreted as a legal representation of legal ownership boundaries.


Site objectives

Manage the site as a preserve for inland beach, northern dry forest, and Fassett's locoweed, and as an aquatic preserve. Natural processes will determine the structure of the natural communities, along with prescribed understory manipulation (see below) in the dry forest. Provide opportunities for research and education on the highest quality native ecosystems.

Management approach

The native aquatic species are managed primarily passively, which allows nature to determine the ecological characteristics of the lake. If lake levels remain low for several years concurrently, however, cottonwood and other woody species may need to be removed from the beach area where the locoweed grows. In the dry forest, the native dominant tree species (primarily pines and oaks) are managed passively. However, understory manipulation and shrub control via harvest, brushing or fire may be needed to mimic natural disturbance patterns. Water quality Best Management Practices will be followed during tree harvest operations. This mostly passive canopy management and understory manipulation will determine the ecological characteristics of the forest. When the old field is planted to sand prairie, the native species will be managed actively through tree/shrub control using tree harvest, brushing and especially fire to mimic natural disturbance patterns. Occasional fire-tolerant oaks, pines, and native shrubs may be retained at low densities. An intensive fire management program will be the primary shaper of the ecological characteristics of the prairie planting. Other allowable activities throughout the site include control of invasive plants and animals, maintenance of existing facilities, salvage of timber after storms, and access to suppress wildfires.

Site-specific considerations

  • The old field will be converted to sand prairie with locally-collected seed.
  • Roadside easement areas may be managed sporadically by township and state.


Very few State Natural Areas have public facilities, but nearly all are open for a variety of recreational activities as indicated below. Generally, there are no picnic areas, restrooms, or other developments. Parking lots or designated parking areas are noted on individual SNA pages and maps. Trails, if present, are typically undesignated footpaths. If a developed trail is present, it will normally be noted on the SNA map and/or under the "Access" tab. A compass and topographic map or a GPS unit are useful tools for exploring larger, isolated SNAs.

Allowable activities

In general, the activities listed below are allowed on all DNR-owned SNA lands. Exceptions to this list of public uses, such as SNAs closed to hunting, are noted under the "Access" tab above and posted with signs on site.

  • Hiking
  • Fishing
  • Cross country skiing
  • Hunting
  • Trapping

Prohibited activities

  • Camping and campfires
  • Collecting of animals (other than legally harvested species), non-edible fungi, rocks, minerals, fossils, archaeological artifacts, soil, downed wood, or any other natural material, alive or dead. Collecting for scientific research requires a permit issued by the DNR
  • Collecting of plants including seeds, roots or other non-edible parts of herbaceous plants such as wildflowers or grasses
  • Geocaching
  • Horseback riding
  • Rock climbing
  • Vehicles, including bicycles, ATVs, aircraft, and snowmobiles except on trails and roadways designated for their use

For rules governing state-owned SNAs and other state lands, please consult Chapter NR 45 Wis. Admin. Code [exit DNR]

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Last revised: Thursday, October 11, 2018