What Is a Prairie?
Types of Prairies
Prairie Protection
Reconstruction Methods
Prairie Resources
Great River Greening helps public and private landowners to restore and manage prairie remnants and reconstructions. Our staff of ecologists, field managers, restoration technicians and landscape designers work with clients to analyze and inventory plant communities, write management, restoration and planting plans, remove exotic and invasive species and manage prairie remnants and plantings. Great River Greening's field staff are trained and licensed to carry out management activities such as chain sawing, herbicide application and prescribed burning.
What Is a Prairie?
Great River Greening uses the French word prairie as ecologists do: to refer to a plant community dominated by native grasses and enriched by many kinds of sedges and wildflowers. Prairies are found coast to coast but are most prevalent in the Great Plains. In historic times these native grasslands stretched for many miles, broken only by wetlands and river floodplain forests. The Twin Cities developed in a landscape that was a complex mosaic of forest and grassland-part of the transition zone between the open prairies and the eastern forests.
Since European settlement, nearly all of Minnesota's prairies have been plowed for agriculture. Many of these fields have been retired from cultivation in recent decades and are now dominated by smooth brome, Kentucky bluegrass and other plants brought in from Europe and Asia. These Eurasian plants are often referred to as exotics or invasives. In the Twin Cities metro region, only a very few small patches of native prairie remain, and most are seriously threatened by invasive species.
Exotic trees and shrubs, like Siberian elm, and native trees, like boxelder, are also invading remnant prairies. In the absence of fire, woody plants will eventually shade out prairie plants. In the past, many of the prairies in this region were maintained by fire. Today, managers of native and reconstructed prairie plant communities use fire, mowing and hand cutting to maintain the open prairie.
Types of PrairiesThere are three general types of prairie in Minnesota: wet, mesic (having moderately moist soil) and dry.
- Wet prairies occur in shallow wetlands that are dry enough to support prairie grasses like big bluestem and switchgrass. Prairie cordgrass and blue-joint are often the dominant species. Wetland wildflowers are abundant, including New England aster, giant sunflower and gay-feather. Wetland alterations such as draining and filling have made wet prairies extremely rare in the metro region.
Mesic prairies are found on dark, rich soils prized for agriculture. They have a dense cover of tall grasses such as big bluestem and Indian grass along with forbs such as purple prairie clover and heart-leaved alexander. They were found along the Mississippi River from St. Anthony Falls to Anoka and Sherburne counties.
Dry prairies are more sparsely vegetated grasslands, sometimes with exposed patches of bare sandy or gravelly soil. Dry prairies vary according to soil, substrate and topography, and they are divided into three major subtypes:
- Barrens prairie is the least common type of dry prairie, mainly occurring on sand dunes in Anoka County. They have sparse cover of grasses and sedges scattered or in clumps. Sand reedgrass, porcupine grass, little bluestem, rigid sunflower and hairy puccoon are typical species.
Sand-gravel prairie is the most common type of dry prairie, occurring throughout the region but especially on mixed sand and gravel soil in southern Washington County, Anoka County and along Mississippi and Minnesota river terraces. Sand-gravel prairies have many species in common with mesic prairies such as big bluestem, little bluestem, butterfly milkweed, leadplant and purple prairie clover, but they are generally sparser and shorter in stature.
Bedrock bluff prairie is found on rocky bluffs and has often been called "goat prairie." It is most common in southern Washington County. Little bluestem, side oats-grama, hairy grama and plains muhly dominate particularly dry slopes and rock ledges.
Prairie Protection
Reconstruction and restoration: Although the terms are often used interchangeably, prairie "reconstruction" and "restoration" have distinctly different meanings. According to the Minnesota DNR, "Prairie reconstruction or planting refers to reestablishing native plants such as prairie grasses and flowers on a site that probably grew there before being eliminated by lawns, crops or other development.
"A prairie restoration, on the other hand, refers to an existing native prairie remnant, a small piece of prairie that has never been completely eradicated, that is being managed to improve the native prairie plant community. Removing problem species, reintroducing fire and possibly adding seed or seedlings are the management tools used to supplement existing species diversity" (from Going native: a prairie restoration handbook for Minnesota landowners. Minnesota Department of Natural Resources, 2000).
The value of protecting and restoring prairie remnants and reconstructing prairie plant communities in areas where no native prairie remains is multifaceted. Established vegetation protects soils and streams by reducing erosion and allowing rainwater to slowly filter into and through soils. Wildlife use these areas for shelter, nesting and feeding. Native plants may contain yet undiscovered compounds with potential medicinal value or have properties that could be used for improving agricultural crops. Native plant communities harbor some of the last populations of rare and endangered plants and animals. Both native remnants and reconstructed prairies provide a glimpse of what much of Minnesota looked like in centuries past. Visitors can enjoy the colors and textures of prairie flowers and grasses and observe the variety of birds and butterflies attracted to these native plants. In residential or recreational areas, small prairie restorations or gardens can create continuity with prairies in surrounding natural areas. Prairie gardens provide an important educational resource by introducing people to grasses and wildflowers that grew in Minnesota before European settlement.
Reconstruction Methods
The first step to prairie restoration or reconstruction is knowing what the existing conditions are before beginning. This is critical if native vegetation is present, particularly if it is extensive or contains rare plant populations. Protection and restoration of a degraded prairie remnant requires a different application of techniques than the ones outlined below. If no significant prairie plant populations are present, reconstructing a prairie plant community would be appropriate. An experienced botanist or ecologist should be consulted to determine what types of vegetation are present.
Methods of reconstructing a prairie plant community vary from site to site, but the basic steps outlined below should be followed when the area has little or no native vegetation. Equally important to perpetuating a prairie planting is proper long-term maintenance to prevent invasive species from becoming established.
1. Site preparation and planting
- Mow or burn the area in spring.
- When regrowth of vegetation is vigorous, spray with glyphosate (marketed under the brand names Roundup® , Kleenup® , Silhouette® , and others).
- When the vegetation is sufficiently brown, burn it off.
- If sufficient regrowth occurs, spray again (early summer at the latest).
- Determine the appropriate seed mix, depending on site conditions and the prairie type best suited to them.
- Sow the seed into the blackened soil by broadcasting or using a seed drill designed for prairie seeds.
2. Establishment and maintenance
- For the first two years mow as frequently as necessary to prevent non-native grasses and weeds from setting seed and shading out native seedlings. It is important to mow at a height just above the native seedlings. This height can range 4-6 inches for some of the first mowings to 10-12 inches, as native plants become taller. Use a flail or mulching mower to scatter the clippings and prevent smothering of the prairie seedlings.
- When enough dry dead grasses from past years' growth have accumulated and enough of this fuel is present to carry a fire, burn the restored prairie in spring. Burn when new growth on the non-native grasses is 8-10 inches tall.
- Burn each spring thereafter if enough fuel has accumulated.
- When native grasses have achieved 80% cover, divide the site into 2-3 burn units, and burn each unit every 3-5 years to set back invasive species, including exotic grasses, trees and shrubs. Burns can be conducted in either spring or fall depending upon the condition and management issues of the planting. To promote diversity, never burn more than one-third to one-half of the site. The unburned areas will provide winter cover, food and a haven for beneficial insects and other wildlife.
- Treat discrete clumps of invasive species (including trees like boxelder) chemically or mechanically if they are not controlled by fire.
- Survey the restored prairie annually for invasive species. Mark discrete patches (with flags, for example) for treatment, and monitor the results.
- Monitor the percentage of native grasses and forbs by surveying at least 30 randomly placed plots (1m x 1m) throughout each type of restored prairie and estimating the percent cover of native plants in each plot.
3. Increase species diversity
- When native prairie species have achieved dominance (greater than 80% cover) in the reconstruction, select additional species suitable for the prairie type.
- To augment the planting overall, rake seed into the ground after a burn.
- If there are patches where natives have failed to establish, prepare for sowing by tilling or digging to create bare soil. Use a rototiller, 2-person auger or shovel to turn the soil then smooth the surface with a rake.
- Spread a small handful of seed into the bare patch, rake seeds lightly into the soil, and tamp down gently. If possible, water the area if rain is not in the forecast.
- An alternative is to install nursery plants rather than seeds in the prepared soil. These require more water.
Prairie Resources
Native plants of the Great Plains
Information about many native plants that grow in the Great Plains is available at these web sites:
U.S. Geological Survey
North Dakota State University
Invasive species
See Great River Greening's fact sheets on exotic and invasive species. Information about invasive species is also available at:
The Nature Conservancy
National Park Service
Restoring and reconstructing prairie plant communities
Two good resources on reconstructing prairie plant communities and restoring remnant prairies are:
- Going native: a prairie restoration handbook for Minnesota landowners, Minnesota Department of Natural Resources, 2000. 52 pp. Available on the web at: MN Department of Natural Resources
- The tallgrass restoration handbook, edited by Stephen Packard and Cornelia Mutel, Island Press, 1997.
The Minnesota Department of Natural Resources has some general information about landscaping with native plants and a link to native plant suppliers and contractors.
Another list of businesses that supply native plants and install prairies is available on the web site of the Minnesota Native Plant Society
This prairie information is also available as a Word Document.
