Criteria

CRITERIA FOR INCLUDING A SPECIES AS A NON-NATIVE INVASIVE SPECIES OR A POTENTIALLY INVASIVE SPECIES IN CONNECTICUT

These criteria were developed in order to objectively list vascular plant species* that are invading minimally managed habitats. They were developed by the George Safford Torrey Herbarium at the University of Connecticut and reviewed and improved by input from many scientists, conservation professionals and nursery representatives. Additional input came from the Connecticut Invasive Plant Working Group, State Geological and Natural History Survey of Connecticut, the Connecticut Biodiversity Forum and most significantly the Definition and Criteria Sub-committee of the Massachusetts Invasive Plant Committee. This last group includes representatives from the Nursery Industry. These criteria have been adopted in Connecticut and Massachusetts and proposed as the national model by the American Nursery and Landscape Association. Tabular summary of how the criteria work.

For a species to be included as a Non-native Invasive Species or as a Potentially Non-native Invasive Species, it must be substantiated by scientific investigation (including herbarium specimens, peer-reviewed papers, published records and other data available for public review) to be:
1. Non-indigenous to Connecticut.
2. Naturalized.
3. Have the biologic potential for rapid and widespread dispersion and establishment.
4. Have the biologic potential for dispersing over spatial gaps away from site of introduction.
5. Have the biologic potential for existing in high numbers away from intensively managed artificial habitats.
Further, to be included as a Non-native Invasive Species, a species must be documented to:
6. Be widespread in Connecticut or at least common in a region or habitat type(s) in the state.
7. Have numerous individuals in many populations.
8. Be able to out-compete other species in the same natural plant community.
9. Have the potential for rapid growth, high seed or propagule production and dissemination, and establishment in natural plant communities.

There are two subdivisions of Non-native Invasive Species. Those that are currently invasive, cause serious management concerns or pose a serious threat to the biological diversity of the state and are widespread in Connecticut are designated as Widespread and Invasive. Those that are equally invasive but currently have a restricted distribution in Connecticut or occur only in a particular region or habitat type in the state are designated as Restricted and Invasive. Species in the latter category may be reclassified as Widespread and Invasive if new populations are found or numbers of populations increase throughout the state.
10A. To be considered as Widespread and Invasive, a species must be widespread in Connecticut with many populations in minimally managed natural habitats.
10B. To be considered as Restricted and Invasive, a species must be common in at least part of the state or a particular habitat type(s) in the state and with some populations in minimally managed natural habitats.If a species meets the initial 5 criteria but does not, at this time, meet Criteria 6-9 (all), it may be included as a Potentially Invasive Species if it meets at least one of Criteria 11-13.

In the past, some of these species have been considered invasive in Connecticut, at least in part because they are known to be invasive in other regions and thus expected to be so here.
11. Have some populations in Connecticut that have high numbers of individuals forming dense stands in minimally managed habitats.
12. Have the potential, based on its biology and its colonization history in the northeast or elsewhere, to become invasive in Connecticut.
13. Be acknowledged to be invasive in nearby states but its Connecticut status is unknown or unclear. This may result from lack of field experience with the species or from difficulty in species determination or taxonomy.
*Species as used here includes all subspecies, variety, forms and cultivars unless otherwise noted.

12 FEB 2000
Leslie J. Mehrhoff
George Safford Torrey Herbariu Box U-43
University of Connecticut
Storrs, CT 06269-3043
(860) 486-5708 FAX (860) 486-6364