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Vegetation Management Guideline by the Illinois Natural History Survey

In my mind, [for a plant to become exotic/invasive] it is a two-part answer. Exotic means that the plant is not native. That is not necessarily a bad thing. For example, tulips are not native and therefore exotic plants in Illinois. But, they are not invasive, meaning they do not establish beyond what was intended. Plants become invasive when they naturalize themselves beyond what was intended. This becomes problematic when they out compete native plants for water, nutrients, and space to grow. In many situations, the invasive plants will provide no value of food or shelter for wildlife and completely alter the environmental dynamics of an area. Potentially, the introduction of an exotic/invasive plant can displace both native plants and animals by disrupting the ecological balance.

Those plants you see listed in the Vegetation Management Guideline are there because they have been recognized as established or naturalized in Illinois. Many of the plants can be found in natural areas such as woodlands, wetlands, prairies, or in disturbed sites such as along roadsides, pastures, and agricultural fields. The Illinois Natural History Survey does a great deal of research in this area, both in identifying exotic/invasive species and how to manage these populations.

Chris Hilgert
Unit Educator Horticulture
University of Illinois Extension Knox County
Email contact 11-3-05

This list was developed by staff of the Illinois Nature Preserves Commission in consultation with staff of IDNR formerly known as District Heritage Biologists (now Restoration Ecologists).  These species included were those perceived by natural areas managers as those imposing the greatest threats to the integrity of natural areas in the State.  This list is distinct from the IL Dept. of Ag's Illinois Noxious Weed Law, which includes some notoriously aggressive species in the agricultural landscape, some of whom also can be problematic in natural areas.  This latter list includes only 8 species; one is native to IL while the remainder are exotics.

[In order to decide what plants make it onto the list] It really is an ongoing effort guided by a panel of experts.  I think there is also an IDNR task force in Springfield that meets periodically.  However, I think much of the work has been done by IL Nature Preserves Commission staff in terms of the control circulars that have been developed and are included at the INHS web site.  Starting first with the obvious choices and adding species as risks become more evident and the need for recommendations on control more urgent.  The criteria are based on invasiveness in natural areas.

Dr. John B. Taft
Senior Research Scientist
Illinois Natural History Survey
1816 S. Oak Street
Champaign, IL 61820
Email contact 1-25-06