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Invasive Species Assessment

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The assessment criteria have been adopted from current available invasive assessments (Fox et al. 2005; Morse et al. 2004; Schutzki et al. 2004; and Warner et al. 2003) and modified for use in the North Carolina horticultural trade. Criteria are those that are likely to have resources and information available for a variety of species. The model is largely non-predictive and not intended to predict invasive attributes or prescreen species not currently utilized in the North Carolina horticultural trade; however, potential for further spread of existing species is considered.

Project Description

An Invasive Species Assessment System for the North Carolina Horticultural Industry was developed by Clara Trueblood as part of a Master’s Thesis project in the Department of Horticultural Science at North Carolina State University.

The North Carolina Nursery and Landscape Association (NCNLA) supported the development of an invasive assessment protocol designed to systematically assess the potential invasiveness of ornamental plants suspected to affect natural areas in North Carolina.

The North Carolina protocol incorporates and builds upon elements of existing assessment models to evaluate the potential invasiveness of plant species in accordance with regional environmental conditions.

The North Carolina assessment criteria are based on a framework of weighted sets of indices that evaluate and rate:

  • Ecological Impacts
  • Current Distribution and Potential for Expansion
  • Management difficulty
  • Benefit and Value

According to the combined weighted results, the model generates a recommendation for evaluated species ranging from ‘unlikely to be invasive’ to ‘invasive and not recommended for use.’

The assessment model incorporates a unique cost/benefit analysis and weighs economic benefits against the ecological risk of selling potentially invasive ornamental plants (Economic Impact Analysis).

The assessment protocol was used to evaluate the invasiveness of 25 nonnative taxa (Summary of Assessment Results).

By modifying the criteria utilized in existing assessments and tailoring the model for the North Carolina horticultural trade, we have created an assessment system unique to the nursery industry that may be completed using resources available in North Carolina.

The assessment results are intended to allow the NCNLA to advise their members regarding plants that are purported to be invasive.

For additional background information, please see the Project Scope and Justification.

Detailed Species Results

The invasive species assessment system for the North Carolina nursery industry provides detailed species evaluations and associated assessment points.

Highly Invasive Species
Vitex rotundifolia (Beach vitex) 81
Lonicera japonica (Japanese honeysuckle) 75
Celastrus orbiculatus (Oriental bittersweet) 71
Moderately Weedy Species
Ligustrum sinense (Chinese privet) 66
Berberis thunbergii (Japanese barberry) 61
Hedera helix (English ivy) 49
Pyrus calleryana (Callery pear) 43
Mahonia bealei (Leatherleaf mahonia) 42
Euonymus alatus (Burning bush) 41
Wisteria floribunda and/or W. sinensis(Japanese and/or Chinese wisteria) 37
Nandina domestica (Nandina, Heavenly bamboo) 35
Ligustrum japonicum (Japanese privet) 34
Noninvasive Species
Elaeagnus pungens and Elaeagnus x ebbingei (Thorny elaeagnus) 33
Spiraea japonica and/or S. x bumalda (Japanese spiraea) 33
Albizia julibrissin (Mimosa) 31
Ulmus parvifolia (Chinese elm, Lacebark elm) 31
Buddleja davidii (Butterfly-bush) 26
Vinca minor (Common periwinkle) 26
Miscanthus sinensis (Chinese silvergrass) 18
Magnolia stellata (Star magnolia) 12
Ginkgo biloba (Ginkgo, Maidenhair tree) 4
Styrax japonicas (Japanese snowbell) 4
Camellia japonica (Camellia) -1
Evergreen azaleas -2
Ophiopogon japonicus and Liriope species (Mondo grass, lily turf, liriope) -5


Literature Databases


Current Federal and State Regulations

Ecological Impact

Distribution and Potential for Expansion

General Resources

(Ecological Impact, Distribution, and/or Management Difficulty)

Assessment Systems