Illinois Technical Resources

Illinois Native Plant Guide

Preferred Water Depth and Inundation Tolerance

This section provides information on the depth of water that each species is thought to tolerate, as well as the ideal or “preferred” depth where known.

Wildlife Value

All of the plant species in this Guide provide some habitat and are valuable for wildlife. Native vegetation provides much better habitat for all types of wildlife than mowed turf grass, rip-rap, or seawall. Information under this item identifies wildlife that is associated with that plant species. In some cases, a particular plant species is required to complete a portion of the life cycle, in others it simply provides the “preferred” habitat. [Back to top.]

Application/Zone

Information provided indicates the role or uses individual species have been observed to provide in reducing soil erosion. All species in this Guide provide some erosion control benefits, but this entry provides specific information on the application or zone where the species is best suited. Note that recommended species mixes for different settings are also provided. [Back to top.]

Availability, Establishment, & Maintenance

Availability refers to the ease of obtaining seeds, or rootstock from commercial vendors. Many native species are not widely available in the landscaping trade, so an effort has been made to select species that are known to be available from some native plant vendors. See Appendix A for a listing of known vendors. Establishment refers to requirements for plant species to be successfully established in an area. This includes various germination requirements for a species. This information is important in order to avoid wasting plant material due to a lack of information on various treatments that may be required. Information is also included about survival rates and what type of propagation works best for a given species. Some species require cuttings, plugs, or root stock, while others are readily established from untreated seed. Finally, information is provided on any long-term maintenance or management concerns or requirements for each species. [Back to top.]

Mature Height

This category provides a range which indicates the height above ground that a plant species may achieve when mature. Note that many deep-rooted native species can take several years to achieve full stature above ground, due to their growth strategy of putting down a deep root system first. This is the primary reason native plants can be very effective at reducing soil erosion. [Back to top.]

Plant Type

Information is provided on whether a species is annual, perennial, biennial and whether it is a shrub, tree, grass, sedge, or forb. See the glossary for definition of terms used for this information. [Back to top.]

Indicator Status

This refers to the wetland indicator categories published for all wetland plant species in the U. S. Fish and Wildlife Service’s National List of Plant Species that Occur in Wetlands: North Central (Region 3). The categories are based upon the probabilities that each species would occur in a wetland habitat. For example, those designated OBL are thought to occur in wetland habitats more than 99% of the time. See Reed (1997) and the glossary for further information. Two species (Aster laevis, Cornus racemosa) were not given an indicator in Reed (1997), so the indicator categories for these two species from the previous version of the list (Reed 1988) are given in brackets. [Back to top.]

pH

PH is a measure of the soil acidity/alkalinity. Information is provided on the pH range a given species will tolerate. For many species, specific pH values were found in the literature, however, in some cases local experience suggests that these values may be too narrow. A widely distributed plant species may have different pH ranges or tolerances in different parts of the country, depending on other soil chemistry and climatological factors. [Back to top.]

Nutrient Load Tolerance

Native plants typically do not require fertilization to become established in a restoration. Experience in prairie restorations in northeastern Illinois suggests that fertilizing native plantings adds to weed problems and promotes undesirable species. For this reason, fertilizing, as in traditional landscaping, is not recommended for native plantings. Information provided under this heading refers instead to the species tolerance of excess nutrient input. High nutrient input from lawn fertilizer runoff, septic fields, or livestock yards can be detrimental to many native species. In this Guide, plant species are rated as having low, moderate, or high tolerance of excess nutrient input. The species included are those natives that are at least somewhat tolerant of disturbed, man-made environments. Those conservative species that survive only under pristine, natural conditions were not included. Thus, of the species listed, those rated as having a low tolerance for nutrient loading would be the least tolerant to high nutrient inputs. Those rated with high tolerance are those most likely to withstand relatively high nutrient levels from a direct source. A moderate rating indicates an intermediate level of tolerance. High, moderate, and low are relative terms that do not consider quantitative values and relate only to the species within this Guide. [Back to top.]

Salt Tolerance

This category provides general information on the salt (NaCl) tolerance of the species. In a few cases, quantitative values were reported in the literature, but in most cases general salt tolerance is provided based upon local observations. A scale of not tolerant, low, moderate, or high was used, based on local observations in road ditches. Again, low, moderate, and high are relative terms that do not correspond to any quantitative values. Please see discussion of these terms under the Nutrient Load Tolerance section on the opposite page. In northeastern Illinois, chloride concentrations from de-icing salt can range from as low as 20 ppm in an isolated natural wetland to as high as 3,000 ppm in a constructed wetland along a multi-lane expressway. [Back to top.]

Siltation Tolerance

The section provides general information on the siltation tolerance of a species. This is based largely upon local observations of species that survive in disturbed habitats where siltation is present. It should be noted that this applies to mature plants, and that young plants can be easily killed if subjected to siltation at an early stage. This problem can be very pronounced for establishment from seed. Jurik et al (1994) found that for many native wetland species, seedling emergence was significantly reduced with as little as 0.25cm of silt. This study was conducted using seeds in a native soil seed bank, but clearly has ramifications for seeds of native species sown in an area subject to siltation. This fact stresses the importance of providing adequate soil erosion and sediment control on project sites. High, moderate, and low tolerance ratings are given as relative terms. See discussion of these terms under the section on Nutrient Load Tolerance. [Back to top.]

Flowering Color and Time

Information is provided on flower color and the time of year one can expect the mature plants to flower. For some users this information may assist in plant selection, arrangement, or planning. [Back to top.]

Light Preference

Information is given as to the shade or sun preference or tolerance of each species. [Back to top.]

Seeding Rate

A range of recommended seeding rates in lbs/acre is provided for each species. Seeding rates for any species depends on the mix of species, setting, and desired result. In order to establish a dense, single-species stand, seeding rates would be heavier than that needed for a mixed species planting. Many plant vendors and installation contractors do not provide seeding rates in their catalogs as they want to adapt rates to each site or they consider rates “trade secrets.” Seeding rates provided in this Guide are ranges taken from three local sources that have experience in the establishment of native plantings in northeastern Illinois. Consideration of the setting, goals and objectives, and best professional judgement should be used in determining final seeding rates for any given project. This information applies only to those species where seeding is appropriate and does not apply to rootstock, transplant, or other planting methods. All rates are pure live seed (PLS). [Back to top.]

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