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Wisconsin State Natural Areas Program Avoca Prairie and Savanna (No. 68)

Avoca Prairie and Savanna

Photo by Thomas A. Meyer



Within the Lower Wisconsin State Riverway, Iowa County. T8N-R1E, Sections 1, 2, 3, 12. T8N-R2E, Sections 5-8. T9N-R1E, Sections 34, 35, 36. 2,208 acres.

NOTE: There is currently a dispute as to whether the public can use Hay Lane and a neighbor has placed a gate across the road prohibiting access. When this issue is resolved, we will update this page. Please see the "Access" tab for access via the river or lake.



Located on an extensive outwash sand terrace along the Wisconsin River, Avoca Prairie and Savanna contains the largest natural tallgrass prairie east of the Mississippi River. Frequent flooding has created braided stream topography characterized by low, sandy ridges interspersed with small linear wetlands giving a local relief of 4 feet. The moist prairie and wetland swales contain more than 200 species of vascular plants including large numbers of rattlesnake master, Michigan lily, and prairie blazing-star. Big blue-stem, prairie cord grass, Indian grass, and sedges dominate the wet areas while little blue-stem, prairie drop-seed, and June grass are common on the drier ridges. Permanent and ephemeral swales contain aquatic species such as sweet-flag, yellow water buttercup, and common bur-reed. Some of the showy species include sweet grass, white wild indigo, flowering spurge, prairie smoke, bottle gentian, cardinal flower, and swamp candles. Oak openings, with large open-grown black and bur oaks, are an outstanding feature of this natural area looking much as they did during the original land survey of 1833. Even today, from many points on the prairie, the same presettlement character has been preserved, with completely natural vistas still accessible in all directions. Avoca Prairie and Savanna is owned by the DNR and was designated a State Natural Area in 1968.


Driving directions

There is currently a dispute as to whether the public can use Hay Lane and a neighbor has placed a gate across the road prohibiting access. When this issue is resolved, we will update this page.

To access by canoe, put in at the Avoca Lake (Marsh Creek) boat launch and canoe downstream (east) approximately 1.5 miles to the road crossing and culvert. Walk north (~0.3 miles) into the prairie. The site is also accessible by canoe from the Wisconsin River.


Avoca Prairie and Savanna 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 reserve for prairie, oak opening and floodplain forest, as an aquatic reserve and wetland protection site, and as an ecological reference area. Allow for a shifting mosaic of dry-mesic to wet-mesic prairie, southern sedge meadow, shrub-carr and oak opening. Natural processes (especially fluctuating water levels) and prescribed fire will determine the structure of the native communities represented here. Provide opportunities for research and education on the highest quality native prairies and oak openings.

Management approach

The ecological characteristics of the site will be primarily shaped by an intensive fire management program. The native prairie and wetland species are managed actively through tree/shrub control using tree harvest, brushing and especially fire to mimic natural disturbance patterns. Occasional fire-tolerant oaks and native shrubs such as meadowsweet may be retained at low densities. The native dominant savanna tree species (primarily oaks) are managed passively. However, some thinning of the canopy, understory manipulation and shrub control via harvest, brushing or fire may be needed to mimic natural disturbance patterns. The mostly passive canopy management and understory manipulation will determine the ecological characteristics of the oak opening. The native floodplain forest species are managed passively, which allows nature to determine their ecological characteristics. Prescribed fire, however, will be allowed to pass through the floodplain forest, though consumption of fuel here will not be facilitated, other than to secure fire breaks. Other allowable activities throughout the site include control of invasive plants and animals, augmentation of native savanna species after careful review, maintenance of existing facilities, and access to suppress wildfires.

Site-specific considerations

  • Although removal of hazardous trees from over and near trails and field lanes is an allowed activity, manipulation/removal of vegetation and soil disturbance should be minimized to the extent possible.
  • An access lane with a ford across a backwater lake is maintained to Department standards.
  • A decades-long tradition of visitors driving on the prairie has caused extensive environmental degradation to portions of the site. Reclamation activities are addressing this chronic problem.


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