Invasive Non-Native Plants That Threaten Wildlands in Arizona

A Categorized List Developed by the Arizona Wildlands Invasive Plant Working Group
Culmination of a statewide project sponsored by SWVMA

The Arizona Wildland Invasive Plant Working Group (AZ-WIPWG) began meeting in March 2003 to assess non-native plants that occur in and are potentially detrimental to Arizona’s wildlands. Representatives from over 20 federal, state, and local organizations, with experience in invasive species biology, plant ecology, or a related field of interest, participated in this statewide effort. Over the period of roughly two and half years, AZ-WIPWG evaluated 74 species. Findings of AZ-WIPG are summarized in the report: Development of a Categorized List of Invasive Non-Native Plants That Threaten Wildlands in Arizona: Final Report of the Arizona Wildlands Invasive Plant Working Group. Individual species accounts will be posted on the Southwest Exotic Plant Information Clearinghouse website in the near future:

AZ-WIPWG responsibilities included:

  • Propose plants for review consideration
  • Identify knowledgeable individuals to prepare the plant evaluation
  • Review the individual plant assessments and make recommendations and suggestions for completing the evaluations
  • Consider the supporting information and documentation
  • Identify the appropriate score for each
  • Assist in raising awareness of invasive plant issues
  • Ensure consistency throughout the process

Individuals volunteered their time and shared their invasive plant knowledge and experience. For each plant, a designated evaluator(s) compiled the available information and conducted a preliminary assessment using the Criteria (see below). At each meeting, evaluators presented the plant evaluations for review.

AZ-WIPWG applied the Criteria for Categorizing Invasive Non-native Plants that Threaten Wildlands, to assess non-native plants that are established in the wildlands of Arizona, including natural areas and working landscapes. The Criteria had been developed as a science-based assessment protocol through a three-state effort involving Arizona, California, and Nevada, which was completed in February 2003. Arizona’s participation in Criteria development was sponsored by SWVMA. Through AZ-WIPWG’s statewide assessment process, a non-regulatory list, the Invasive Non-Native Plants That Threaten Wildlands in Arizona has been developed, that categorizes plants according to their relative impacts on ecological processes, species, and native ecosystems.

The List is intended to provide useful information to land managers, industry, and other stakeholders in making management decisions. Use of the List is voluntary. Periodic updates to the List may be necessary as new information on listed plants is acquired or as new non-native plants become established in Arizona’s wildlands.

The List goals and uses are:

  • Provide a comprehensive state-wide overview of non-native plants established in wildlands
  • Develop information on the ecological impacts and distribution of invasive non-native plants
  • Influence future additions to regulatory lists
  • Identify and rank by severity category invasive non-native plants occurring in Arizona’s wildlands
  • Facilitate the preparation of environmental documents
  • Provide a means for coordinating activities with adjoining land owners
  • Identify research needs and gaps in current information

The List does NOT:

  • Have regulatory or legal status
  • Provide absolute or static ranks for the species
  • Prescribe management actions or indicate degree of management difficulty
  • Prioritize specific site needs

The criteria and the list are supported by the following organizations:
Arizona Association of Environmental Professionals
Arizona Department of Agriculture
Arizona Department of Environmental Quality
Arizona Department of Transportation
Arizona Department of Water Resources
Arizona Game & Fish Department
Arizona Native Plant Society
Arizona-Sonora Desert Museum
Arizona State Land Department
Arizona State Parks
Bureau of Indian Affairs
Bureau of Land Management
Bureau of Reclamation
National Park Service
Sonoran Institute
Southwest Vegetation Management Association
The Nature Conservancy in Arizona
University of Arizona Cooperative Extension
US Army Corps of Engineers
US Department of Defense
US Environmental Protection Agency
US Fish & Wildlife Service
USDA Forest Service
US Geological Survey

For more information, contact Dr. John Hall at, 520-547-3439 or visit the SWEPIC website at