Selecting the appropriate species of native plants is one of the first steps in planning a reconstruction project. It requires information on site conditions (soil types/moisture, slope, aspect), species characteristics (geographic distribution, light requirements, life span, phenology), appropriate seed sources, and seed cost. All these factors affect the kind and number of species included in a seed mix. Read below on how to choose the best native species for your planting, then try out our Iowa Prairie Seed Calculator to help guide you to a successful seed mix.
Criteria for Species Selection
Soil Type and Moisture - Each soil type is a unique blend of sand, silt, clay, and organic matter that affects how the soil drains and retains water. Every plant species has evolved to grow within a certain range of soil moisture conditions. Planting species that are best adapted to the soil moisture(s) of the site will ensure their persistence in the planting.
Most prairie seed nursery catalogues list the soil moisture preference of each species as: W (Wet) – species adapted to soils that are soggy or wet most of the growing season; WM (Wet Mesic) – species adapted to soils that are wet in spring and winter after rainfall but dry out during the summer; M (Mesic) – species that are adapted to soils that remain moist during the growing season; DM (Dry Mesic) – species adapted to soils that remain dry out between rainstorms; D (Dry) – species adapted to soils that remain excessively dry for most of the growing season.
To determine the soil type of your planting site, visit with your local Natural Resources Conservation Service (NRCS) office to obtain a soil map or use the USDA Web Soil Survey.
Species moisture preference to NRCS soil moisture drainage classification conversion: W (Wet) = very poorly and poorly drained soil types; WM (Wet Mesic) = somewhat poorly drained soil types; M (Mesic) = well-drained and moderately-well drained soil types; DM (Dry Mesic) = somewhat excessively drained soil types; D (Dry) = excessively drained soil types.
- Slope and Aspect - The site conditions on a slope and the direction it faces (aspect) affect the establishment of native plants. The upper portion of a slope is usually drier than the lower portion; south and west aspects are relatively drier than the north and east aspects at the same elevation. Thus, there is a sorting of species along the moisture gradient from top to bottom of a slope and around it as the aspect changes.
- Geographic Distribution - Select species that are native to the region of the planting site. The best estimates of species distribution have been determined through observing local remnants and herbarium collections of plants found in native prairies. A “region” can be defined as the home county and the contiguous counties around it.
- Light Requirements - Light availability in nature is a continuum from full sunlight tallgrass prairies to sun flecks as in a closed canopy forest. Select species that are appropriate to the light conditions of the planting site.
- Diversity - A prairie seed mix that includes species from each plant group (warm- and cool-season grasses, legume and non-legume forbs, and sedges) is more likely to result in a stable, weed-resistant plant community that will attract and sustain wildlife.
- Milkweed for Monarchs - Several species of non-weedy milkweeds are available to support monarch butterflies. If the common milkweed makes you nervous, try using swamp milkweed (wetter ground) or whorled milkweed (dryer soils).
- Phenology - Tallgrass prairie plants exhibit a wide range of growth characteristics. These plants have evolved to take advantage of available resources throughout the growing season. Some grasses and sedges germinate, grow, and flower in spring or fall (cool-season plants), while others germinate in late spring, and grow and flower in the summer (warm-season grasses). For a prairie planting to resist non-native weed invasion, the planting must include native species from both cool- and warm-season grasses, forbs, and sedges. Leaving out any of these groups will expose the planting to weed invasion.
- Life Span - Native plants can be classified as annuals, biennals, and perennials. Annual plants germinate, flower, and die in one growing season. Biennials germinate and remain vegetative in the first year, flower, and die in the second year. The benefits of having native annuals and biennials in the seed mix are three-fold. Annuals and biennials readily germinate and grow large in the first growing season, covering more bare soil and thereby reducing the potential soil erosion. In addition, their rapid growth may reduce weed abundance by competing with weeds for resources in years one and two. Lastly, native annuals and biennials flower by Year 2, creating a native seed bank to recolonize bare soil created by disturbances that could occur in the future. Most native species are perennials; they flower and survive year after year. Perennials provide long-term diversity and stability.
- Appropriate Sources - The source of seed for reconstructing prairie is a growing concern to resource managers. Seed derived from multiple remnant sources within the region of the planting site may be better adapted to the climate and soils of a site than seed from distant sources. Seed used for a native planting should be derived from prairie remnants within the region of the planting site.
- Cost - Another critical factor influencing the number and kind of species included in a seed mix is the cost of the seed. The commercial price for native prairie seed varies greatly by species. In 2007, prairie phlox, Phlox pilosa seed cost $1,760.00/lb compared to ox-eye sunflower, Heliopsis helianthoides seed at $45.00/lb. Deciding how many of the more expensive forbs to include depends upon the seed budget and the preference of the person paying for the seed. Consider including some expensive forbs in seed mixes; costs can be controlled by lowering seeding rates of the expensive species.