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Alien Plants Ranking System

Version 5.1


The system relies on a set of 23 questions (DataSheet) to be answered for each nonnative plant known to occur in (or near) the site of concern. The questions are organized into 3 sections. Section I, which addresses the current level of impacts to the site, must be based upon site surveys. Section II asks specific questions that give indications of the potential of the species to be invasive. For many alien plants, answers to these questions are available within the system (species FactSheets). If this information is unknown, and not available within the system, it should be obtained through library research. Section III poses questions that affect the feasibility (and costs) of control.


Upon completion of the DataSheets for all nonnative species found on a site, the manager can print the following:
  1. Completed DataSheet for each species (Sample)
  2. List of all entered species sorted by level of impact, or potential to be invasive, or feasibility of control
  3. Lists, such as species found to be innocuous, or species causing serious impact, or species not currently causing impacts but having high potential to invade and cause impacts, or some other grouping determined by the user
  4. Graphic depiction of data showing impact, potential to be invasive, and feasibility of control for the suite of species in the data file (Sample)


Individuals who use APRS must be able to interpret specific biological information on each species both in the field and in the literature. It is essential to identify species correctly in the field.


  1. DETERMINE THE NONNATIVE SPECIES that do occur or are likely to occur within the site of interest. Possible sources of lists include research reports for the site or region, catalogs of specimens for regional herbaria, species lists by county from state or county weed boards, or lists from biological surveys or natural feature organizations. Once a list of species is completed, local floras or Kartesz (1994) should be consulted to see which species are nonnative.
  2. SURVEY THE SITE. The best survey method is to conduct quantitative sampling stratified by vegetation type, using a geographical information system (GIS). This not only provides the information to complete Section I of the ranking system but allows for analysis of correlations of distribution and abundance of nonnative species with vegetation type, roads, trails, etc. Sufficient information can, however, be obtained by a less intensive, systematic qualitative survey of the area. The location and extent of nonnative species stands should be mapped.
  3. CONSULT THE SPECIES FACTSHEETS to see whether information to complete Section II (Potential to be a Pest) of the DataSheet is included. Also, consult the FactSheets to obtain information to complete portions of Section III (Feasibility of Control). If a FactSheet for the species is not available, a literature search should be made to gather the needed information for completing Section II and Section III. Keyword searches using the common and scientific names of the species are suggested.
  4. CREATE DATASHEETS for all of the nonnative species found within or adjacent to the site. After completing this step, save as a data file for your site. All of the products listed above can then be generated for the site. Questions that cannot be answered are marked "unknown" in the DataSheet. In the Graphs module, you can visualize how important the answers to unknown questions are in the overall ranking of each species by using the "maximum-minimum" function, which plots the range of possible values for the unknowns.
  5. STUDY THE INFORMATION AND GRAPHS GENERATED and apply them towards the development of a management plan for the site and surrounding area.

Kartesz, J.T. 1994.  A synonymized checklist of the vascular flora of the United States,
     Canada, and Greenland, 2nd Ed. Timber Press, Portland, Oregon.


The Invasive Plants Bibliography is a selected bibliography on species of invasive plants in the upper midwestern United States. These references were used to gather data on botanical characters of alien species in national parks of the region. Data were classified and compiled into data files for use in the Alien Plants Ranking System program. The bibliography focuses on sources containing botanical data, not data on control or management of species, and is not intended to be broad. References consist of books, monographs, and original journal articles. The bibliography is being maintained and added to periodically. The version available here will be updated regularly.

Persons familiar with additional references meeting the above criteria are asked to forward them to Jim Bennett (


Ronald D. Hiebert, National Park Service (system development)
Diane L. Larson, US Geological Survey (team coordinator, field surveys and testing)
James P. Bennett, US Geological Survey (botanical characters research)
David W. Lime, University of Minnesota (consultant)
Anthony M. Starfield, Univ. of Minnesota (consultant)
Jerrilyn L. Thompson, Univ. of Minnesota (customer feedback, fact sheet development)
Diane L. Beres, University of Minnesota (consultant)
Karl A. Beres, Ripon College (system automation)

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