Planting and maintaining a prairie garden

Select a site with the following specifications:

• Full sun with few trees.

• On the east, west or south side of buildings.

• Does not contain weedy vegetation such as quackgrass, Canada thistle, reed canary grass.

• Seek professional help for preparing such a site.

To avoid fire danger:

• Locate the prairie at least 30 feet from buildings.

• Separate the prairie from buildings with an area of gravel, concrete, turfgrass or irrigated plantings.

• Prune live and dead branches of nearby trees at least ten feet above the ground.

Site design

• Check  with your local city government about local weed ordinances before developing a prairie. You may need to apply for variances.
• Some prairies look more natural than other landscapes. Discuss the prairie with neighbors to let them know about the changes you are making and that the site is being maintained.
• Consider using mowed edges, signs, bird houses and edging fences near your prairie to show the area is meant to be there.

Soil analysis

Prairie plants are adapted to specific soil types and moisture levels. Understand the drainage and sun and shade exposure of your site when selecting plants for your location.

• Determine whether you have sandy, clay or loamy soil.

• Have your soil tested at the University of Minnesota Soil Testing Lab to determine the soil pH and organic matter.

• Determine the soil moisture of your site.

  • Dry - draining readily with no standing water.

  • Mesic - medium moisture with some puddles after rain.

  • Wet - wet soil throughout the season with standing water in spring and fall.

Standing water or water that does not drain from a 1-foot-deep hole within 24 hours are indicators of wet and poorly drained soils.

Remove all existing plants to reduce plant competition. New prairie seedlings are not able to establish if they are competing with existing vegetation. Weeds and turfgrasses must be removed. Seed must have good contact with soil for germination.

Three methods to establish a prairie in an existing lawn or area of other vegetation:

• The most common method of establishment uses a nonselective herbicide containing the active ingredient glyphosate to kill all existing vegetation. Follow directions carefully and wear protective gear.
  • Wait 1 to 2 weeks after applying glyphosate. When existing vegetation has died, the soil should be tilled to a depth of 12 inches or more with a rototiller, harrow or disc to incorporate dead material.
  • If a seed drill or slit seeder will be used in planting, tilling may be eliminated and the now dead vegetation mowed to a 1- to 2-inch stubble.
  • After tilling, the site should be raked, either by hand or with a power rake.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.

• Put a dark plastic sheet, tarp or pieces of plywood over the grass for at least two months before you begin planting.
  • All plants will be killed and can be removed. It may be difficult to remove tough perennial weeds like thistles and quackgrass.
  • Once the vegetation is dead, till the area thoroughly.
  • This method works best when begun in the summer or fall to prepare for a spring planting.
• Turn the soil and cultivate the area every few weeks for a complete growing season.
  • Turning the soil brings weed seeds to the surface, and cultivating kills the seeds that have germinated since the soil was last turned.
  • Till to a depth of 12 inches or more and rake the area to create a uniform fine seedbed.

Select plants that will grow well in the sun, shade, soil type and moisture of your particular site.

• Prairies consist of 80 percent grasses and sedges and 20 percent wildflowers or forbs. Include a mixture of warm-season and cool-season grasses.

  • Warm-season grasses predominate in prairies. They are slow to grow in the spring but tolerate summer heat and drought and flower in the late summer and fall.

  • Cool-season grasses grow in early spring and fall but are often dormant in summer.

• Grasses provide physical support, weed competition, protection for wildflowers and a source of food and shelter for birds during the winter.

• A "nurse grass" that germinates quickly may be planted to minimize weed competition during establishment.

• Wildflowers should  be selected based on soil moisture and available sunlight and should include a variety of bloom times to support native insects and butterflies.

Seeds vs. plants

You can start a prairie from seeds or plants. Plants can be used for small areas, however larger areas will require seed for establishment.

• Starting from seed is more economical, but can take two to five years for the plants to reach full size.

• Plants are more expensive, but establish quickly and may flower the first year. Plants can be planted anytime from spring through fall.

Some species are available only as live plants.

• Prairie seed companies create seed mixes appropriate to your site conditions.

  • Consult with local seed dealers to determine the correct mixtures and amounts.

  • Be sure that any seeds you purchase are packaged for the year that you will sow them and list current germination and pure live seed percentages.

• "Seed-in-a-can" wildflower mixes are not recommended as they often contain annual plants and a mixture of seed for all soil types.

• Group several plants of the same species together to make a showy display and to increase pollination and seed set.

Planting grasses

• The best time to sow seed is in the spring between May 15 and June 20. Seed may also be sown in fall, between mid-October and freezing.

• Even seed distribution and good seed-to-soil contact are essential.

• Seed may be broadcast by hand:

  • Mix seed with slightly damp sawdust or peat moss as a carrier.

  • Use one bushel of carrier per 1000 sq. ft. of area.

  • Distribute seed in a broad arc to spread evenly.

• A spreader may be used:

  • Mix seed with clean sand or vermiculite.

  • Make passes in two different directions.

• For larger areas, mechanical planters can be used, including:

  • Tye drill, Truax drill, Rangeland drill.

  • Brillion seeder.

• After sowing, roll seed to improve soil-to-seed contact. Be sure to roll when soil is dry.

Planting wildflowers

• Wildflowers may be sown with grasses or planted one to two years after grasses have been sown.

• Wildflowers are generally sown from seed on larger sites, as this is most economical. Plants will take two to five years to establish and bloom.

• Wildflower seedlings may be planted also. Transplants are more expensive, but establish and bloom quickly.

• Wildflowers may be clustered near paths and residences for best color in these areas.

Seeding rates

• Seeding rate varies by species and seed quality.

  • A general rule of thumb is 30 seeds per square foot.

  • Grasses may be sown as low as 20 seeds per square foot.

  • Forbs or wildflowers as high as 60 seeds per square foot.

  • Consult information on the label for each type of seed you are planting.

  • Hand sowing for small sites may require more seed.

• Get more specific instructions on seeding rates from the information provided when buying seeds.

Watering after seeding improves germination, but is not essential unless no rainfall occurs for several weeks.  

• Cover with a thin mulch of clean, weed-free straw to prevent drying, reduce exposure to wind and animals and to prevent erosion on slopes.
• Prairies usually do not need herbicides, fungicides, insecticides or fertilizers.  
• Weed control in the first two years of a prairie is essential.
  • Hand weeding, burning and mowing are the most effective ways to control weeds.
  • Remove woody plants, such as tree seedlings.
  • Any weeds that are allowed to go to seed will mean more work in the future.
  • Remove weed seed-heads in the first few years to eliminate future problems.

First year management:

• Control weeds by mowing regularly in the first year to a height of 4 to 6 inches. Mowing at this height will reduce weed competition without harming new prairie grasses and wildflowers.

• Do not allow weeds to go to flower and seed. Ideally all weeds can be mowed or removed to grow no taller than 8 to 12 inches.

• Don’t pull weeds by hand as this disturbs new prairie plants and may introduce additional weed seeds.

• At the beginning of the second season, evaluate how many weeds are present. It may be necessary to mow the prairie to 4 to 6 inches the second and third year to keep weeds under control.

  • The goal is to minimize weed and seed set while allowing prairie plants to grow.

  • Prairie grasses develop roots the first few years and grow slowly above ground.

  • By the third year, the plants develop more growth above ground.

Long-term management:

• After the prairie has been established for at least three years, you can maintain the prairie with controlled burns.

• Controlled burns are recommended for larger sites, which are often done on a rotation basis, with 1/3 of the plot mowed annually.

• Burning in April or early May is best for native plants.

• Check with your local fire department and the Department of Natural Resources to get information and required permits.

On smaller sites, mowing is an alternative to controlled burning.

• Mow once a year after prairie seeds have fallen, usually in early spring.

• Remove clippings to expose crowns of plants.