Hole-in-the-Mountain is a large prairie remnant situated on a steep valley along the outer edge of the glacial escarpment known as the Prairie Coteau. Its undulating terrain is carpeted in wildflowers during summer. The preserve provides excellent habitat for rare prairie-dependent insects, including 25 species of butterflies, and nesting waterfowl, passerines and other grassland birds. The prairie valley is the headwaters of Flandreau Creek, which runs in a southwesterly direction toward the Big Sioux River. Indians called the half-mile-wide valley "Mountain Pass" or "Hole-in-the-Mountain."
Why the Conservancy Selected This Site
Hole-In-The Mountain Prairie is a remnant of what was once a 4,300-acre prairie landscape. Much of the surrounding land is in private agricultural use. When the first tract of the preserve was acquired by The Nature Conservancy in 1978, most had been altered to some extent from their pre-settlement condition. Historically, most of this area had been used to pasture sheep and cattle on the steep slopes and parts of the floodplain. Upland flats were cultivated.
What the Conservancy Has Done/Is Doing
This preserve is managed by prescribed burning and the native prairie vegetation on the steeper slopes has recovered well in recent years. Areas of old fields have been replanted to native species. Several tracts adjacent to the preserve have been purchased by the Conservancy and transferred to the Department of Natural Resources and are managed for wildlife and natural area use.
What to See: Plants
During settlement, the vegetation here began shifting from taller prairie grasses such as big and little bluestem and Indian grass to drier species characteristic of prairies further west such as needlegrasses, wheatgrasses, and grama grasses. Now the preserve harbors more than 60 species of grasses, sedges, and rushes, 10 species of trees and shrubs and 200 species of wildflowers. Native plants include six of special concern: prairie moonwort, small-leaved pussytoes, small white lady's slipper, red threeawn, soft goldenrod, and slender milk-vetch.
What to See: Animals
Most unique to Hole-in-the Mountain are its butterflies, thriving on the native grasses and forbs protected here: The Dakota skipper and Ottoe skipper, both threatened species; and the Uncas skipper (Hesperia uncas), an endangered species. The inconspicuous Dakota skipper butterfly has a wingspan of 1 to 1 1/2 inches, is yellow or straw colored, and has an erratic darting flight. It was first discovered near Volga, South Dakota and survives on only a few scattered virgin prairie habitats in the Dakotas, Iowa and Minnesota.
For more information on visiting this and other Minnesota preserves, check out our Preserve Visitation Guidelines.
From the City of Lake Benton, go south on U.S. 75 for 1.5 miles and park at the turn-out along the west side of the highway. The best time of year to visit is spring through fall, during the wildflower blooming season. (1.5 miles south of the city of Lake Benton.)