IPAW Working List of the Invasive Plants
of Wisconsin - March 2003

Introduction

The mission of the Invasive Plants Association of Wisconsin (IPAW) is to advance understanding of invasive plants and encourage their control to promote stewardship of the natural resources of Wisconsin. A recognized key to accomplishing this mission is to develop a working list of the plants that are invasive in the natural plant communities and wild areas of the state. A listing of the invasive plants of Wisconsin will serve several useful functions. As stewards of the natural and wild areas of the state, many of us have watched some plant species become established and begin to spread at our sites long before we became aware that the species was already known to act invasively in natural communities. A list will provide a reference for species that we should consider managing at an early stage of establishment while they can be effectively controlled.

This list will give IPAW a focus for our educational efforts. This working list also represents a call for more information about the ecology, distribution, and control of the listed species. Several species on the list are well known to be seriously invasive, and there is a considerable amount of information about the habitats they invade, their distribution in the state, and methods for their control. Many other species on this working list have been observed to be aggressive invaders somewhere within the state, but little information has been compiled about just what native plant communities are at risk or effective methods for management. IPAW is committed to maintaining this list to reflect the most current information available on the invasive plants of the state.

As more information is obtained some species will undoubtedly be added to the IPAW list of known invasive plants. Other species may be removed when it is revealed that they do not pose the threat currently thought to exist.

IPAW has already developed clear definitions of various categories of troublesome plants:

• Invasive Plants are non-indigenous species or strains that become established in natural plant communities and wild areas and replace native vegetation.
• Weeds are undesirable and troublesome plants growing in disturbed areas, especially cultivated ground.
• Potentially Invasive Plants (for Wisconsin) are species that are invasive in parts of North America having similar climates and plant communities, and that are thought to have the potential to colonize and become invasive in Wisconsin.
• Sometimes Invasive Natives are native plants that can become overly abundant in a plant community to which they are indigenous, often in response to a change in the disturbance regime.
• Indigenous means occurring naturally in a specific area or plant community, not introduced.

The "IPAW Working List of the Invasive Plants of Wisconsin" is presented here.

This list is not intended to include weeds, nor does it include plants that are native to the state. A list of the worst agricultural weeds of Wisconsin would be useful to some groups in the state, but the focus of IPAW is plants that invade natural plant communities, and combining a list of weeds with a list of invasive plants has the potential to create considerable confusion. If a need is demonstrated for IPAW to catalogue the weeds of the state, formation of that list will be a separate project. There are of course some species that are both invasive plants and weeds (e.g. Canada thistle, Cirsium arvense), and these are catalogued on this working list. Those non-native species that are not known to be currently invasive in Wisconsin, but that are invasive in similar ecoregions and may have the potential to become invasive in the state, are presented separately in the "IPAW Working List of the Potentially Invasive Plants for Wisconsin".

A PDF version of these lists is available in Newsletter Issue 4 - March 2003 (PDF, 328KB)

For a technical description of the methods used to develop The List, see the Methods page.