Designing Seed Mix

"Designing a proper seed mix plays a pivotal role in establishing a high-diversity, low-maintenance prairie restoration" (Packard).

Several factors were considered when designing our original seed mix including:

Site Conditions

Since our site was previously an agricultural plot (corn and beans) our goal was to introduce a majority of forbs and grasses that were known to exist on black soil prairies (mesic) in Sangamon County and Central Illinois. Our site receives full sun and has a uniform soil and slope which allowed us to choose from a large variety of seed that produces mesic prairie plants. Our site is easily accessible and located on an area of campus that should not be threatened by new buildings or other types of expansion projects.

Site Goals

The main goal for our site was to produce a simulation of a tallgrass mesic prairie with few or no trees. We also wanted to produce a high quality prairie consisting of a  large variety of native forbs to Central Illinois and Sangamon County. Our goal was to create an ecologically functioning prairie, not just an aesthetic wildflower and tallgrass garden.

Seed Selection

Prairie seed should be of high quality and should originate within 200 miles of the planting site (Robertson). Some individuals believe that it is best to purchase or collect seed from a site that is within 100 miles of the restoration site in order to preserve the integrity of local plant populations (McClain). Fortunately, there are several reputable suppliers of locally collected seed that we could choose from. Important factors considered when discussing seed quality included:

1. Contact the Illinois Department of Conservation for info on the reputation of local suppliers

2. Is the source of the seed from nursery grown plants or collected from prairies?

3. If collected from prairies, are they local? Regional?

4. Was the seed treated (stratified)?

Seeding Rates

The seeding rates per acre are sometimes referred to as the grass-to-forb ratio. For a pure stand of grass, a seeding rate of 8 to 10 pounds per acre should be sufficient. For a mixed stand with numerous prairie forbs, reduce the amount of grass seed to 2 to 4 pounds per acre, particularly the larger grasses such as Indian grass and big bluestem. Increase the amount of forb seed until the mixture is about 60 percent grass and 40 percent forbs by weight.  Mixes with lower percentages of forbs (20-40 percent by weight) tend to result in grass-dominated prairies in a very short time. On the other hand, mixes with larger percentages of forbs (50-60 percent by weight) usually produce a more diverse prairie community with a good cover of both grasses and forbs. Mixes with more than 70 percent forbs can lead to poor burns. Taking these recommendations into consideration, and opting for a more diverse prairie, we decided to keep the grass-to-forb ratio generally at 50-50 for the original planting as well as all future seed plantings.

Budget 

The available funds to support the UIS Prairie Project came from monies raised from bake sales, environmental t-shirt and button sales, and from grants received by the Student Life Office that were available to official, organized student clubs. SAGE became an official student club in 1990 during the 20th anniversary of Earth Day. The UIS Department of Physical Planning and Operations offers several free resources and services to SAGE including plowing, mowing, equipment and supplies, and vehicles. The Illinois Department of Natural Resources provided SAGE with burn equipment when needed until we were able to purchase our own. 

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Seed Suppliers

Since  prairie restorations have become more popular, restorationists and seed suppliers harvest and clean thousands of pounds of seed for prairie, wetland, and savanna restorations. UIS obtained seed from several sources throughout the history of the prairie including:

Two of our suppliers, Prairie Frontier and Prairie Moon Nursery, were outside of the 200 mile range, however, Prairie Moon Nursery obtains much of its seed from Illinois prairies, and Prairie Frontier gave us a good deal on seed cost. We chose only seed from plants that are native to central Illinois from these suppliers. For a  more complete list of prairie seed suppliers:

Below is information on the seed/seedling suppliers that we chose for our site.

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Seed Treatment

The seeds of many native plants have built-in dormancy mechanisms which protect them from germinating before killing frosts or in times of droughts. In the wild, seeds will lie dormant until the proper conditions for growth occur. But in cultivation, a restorationist must become familiar with several simple pre-sowing seed treatment methods which will unlock the dormancy mechanisms and stimulate quicker, more consistent germination.

Most prairie seed needs to be stratified (cold, damp storage) before they will break dormancy. This fact is useful in counteracting the problem of prairie grass outcompeting forbs. Forbs can be stratified for an appropriate time (this varies depending on the species) while grasses are planted without a stratification period. This differential stratification will give prairie forbs an advantage over grasses in the initial phase of establishment. Different species have different germination requirements. In general, seeds must be encouraged to imbibe water, be exposed to proper temperatures, and have proper ventilation and adequate time in order to transform themselves into living plants.

Common Treatment Processes 

Seeds are mixed with damp (not wet) builder's sand, vermiculite, or old sawdust for several months during winter

Seeds are mixed with damp medium and stored for several months at temperatures between 68-75 degrees 

Dried seed is placed in plastic or paper bags and then refrigerated at 34-40 degrees F or just placed in an unheated, insect and rodent-free building over winter

The seed coats are physically broken, using sandpaper, allowing the embryo to imbibe water

Applying a nitrogen-fixing bacteria to wet seed just prior to sowing

Sowing seed along with the seed of a host species or transplant seedlings into pots containing host species

Seed is sown on top of a smooth, firm sedbed and kept moist until germination occurs

For a complete treatment guide for most native prairie plants:

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Seeding Methods

Seed Drill

Seed drills are tractor-pulled farm implements that have a series of small plows or disks that open furrows in the soil, then meter in a specified amount of seed from a top-mounted storage box down tubes into the ground. Seed drills are the most efficient means of seeding a prairie. By accurately placing seed at an exact depth at an even rate across the site, they make the most efficient use of precious native seed. Unfortunately, we were not able to utilize this method because seed drills are very expensive to buy and costly to rent or hire the service.

Broadcast Spreading

Broadcasting seed in spring is the most common method of planting, either by hand or using a lawn-type spreader. Seeds planted in May or June avoid competition with the early, rapid weed growth. This is the method we chose for several years after the first planting, which was done in late fall due to the timing of the decision to start a restoration project. During all plantings, volunteers would broadcast seed by hand and work it into the soil to allow for a good seed to soil contact.  We attempted to use a broadcast spreader, however, the bulky seed would clog it.

Seedlings

The hand-planted seedling prairie represents the ultimate quality control in prairie restoration (Packard). This method has been used on the UIS prairie since 1996 along with broadcast spreading and interseeding. Growing seedlings requires total commitment to watering and weeding the first growing season, but it is almost totally carefree after that. In the spring of 1996, we purchased 750 seedlings from a local grower and planted them immediately into the prairie. The results were impressive with some seedlings blooming the first year. A majority of them are presently thriving and have become hearty, spreading their seed creating  more surrounding plants. This method can be costly (pots and flats), but many supplies can be reused for years. In 1998 and 1999, we germinated and planted over 1000 seedlings that were grown from existing seed from the site. 

Interseeding

Interseeding is a technique where seed is sowed directly into existing vegetation without soil treatment or plowing.  The existing vegetation provides a fuel source for future burns and is eventually squeezed out by the natural natives that are adapted to the surrounding conditions. Interseeding is a good way to restore remnants, and is often a better starting place for seeds than tilled earth. This was the method used for the first planting of the expansion section in 1994. Unfortunately, this section was periled by exotic weeds such as Giant Ragweed and Giant Goldenrod due to a large amount of weed seed leftover from years of farming. This problem has improved from consecutive burns, mowing, more interseeding, and some herbicide spraying. By 1995, there were enough existing plants on our site to generate a substantial amount of seed. Seed has been annually collected in fall, mixed, treated, and interseeded into the existing site either in early winter or the next spring. 

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Seedlings

In 1996, SAGE received grant money from UIS' ICCB to purchase 750 seedlings from the Prairie Patch in Niantic, Illinois. Each species type of seedling was planted in groups of 3 or 4 and surrounded by mulch to decrease competition with weeds. Although this was a very labor intensive activity, the results were very rewarding with an average of 90 percent survival rate. Most of these seedlings began flowering within a year or less, a much shorter time than seen with plants grown directly from seed. In 1998, 510 seedlings were planted after treating and germinating seed that was collected from the prairie site. In 1999, 768 more seedlings were planted on the site from existing seed. In 2000, after an inventory revealed that there were 40 different species of native plants on the site, UIS purchased seed of nearly 40 species that were not present on the site. The seed was treated, planted in pots, germinated, and eventually planted on the site. Nearly 1300 seedlings were planted throughout the spring and summer. For more detailed info on this project, see biodiversity project .