Appendix 1
Maine Criteria for Evaluating Non-Native Terrestrial Plant Species (Draft 12/07)
The following criteria must be met for a species to be considered in any of the three categories (INVASIVE, LIKELY INVASIVE or POTENTIALLY INVASIVE) of invasive plant. The species must:
- Be non-native to Maine.
- Have the potential for rapid growth, dissemination and establishment in minimally managed habitats.
- Have the biological potential for widespread dispersion and for dispersing over spatial gaps.
- Have the biological potential for existing in high numbers or large colonies away from intensively managed artificial habitats.
- Have the potential to displace native species in minimally managed habitats.
Species to be designated INVASIVE must also meet all (6 and 7) of the following criteria.
The species must:
- Be widespread in a region or habitat type(s) in Maine. AND
- Have many occurrences of numerous individuals or colonies that displace native species in minimally managed habitats in Maine.
Species to be designated LIKELY INVASIVE must meet the following criteria.
The species must:
- Be naturalized in Maine (persist without cultivation)
and must meet one of the following criteria (2or3)
- Have at least one occurrence in Maine that has high numbers of individuals forming dense stands in minimally managed habitats. OR
- Have demonstrated to be invasive in nearby states and provinces or areas with similar climates, but its status in Maine is unknown or unclear. (this may result from lack of field experience with the species or from difficulty in species determination or taxonomy)
Species to be designated POTENTIALLY INVASIVE must meet all of the following criteria.
The species must:
- Have no known naturalized occurrences in Maine.
- Have demonstrated to be invasive in nearby states and provinces or areas with similar climates.
- Be anticipated to naturalize in Maine.
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