Exotic Plant Policy and Procedures

Introduction and general policy statement

Invasive exotic plant species have negatively affected the natural function of ecosystems, agriculture and human health world-wide. Humans have and continue to accidentally or purposefully homogenize the world's flora and have forced unlikely species interactions, many of which cause ecological disruption. The deliberate introductions of certain notorious invasive exotics to the southeastern United States, such as kudzu (Pueraria montana), Chinese privet (Ligustrum sinense), bamboo grass (Microstegium vimineum), and Japanese honeysuckle (Lonicera japonica), continue to be disruptive; these species have naturalized to the extent that they are now inextricable from the local landscape. Despite the acute awareness of the negative ecological consequences of invasive exotics, many botanical gardens and arboreta continue to be a source of potentially invasive exotic plant material.

A primary mission of the North Carolina Botanical Garden is to "participate in and promote the conservation of biological diversity." In accordance with this mission statement, our policy with regard to exotic plant species at the North Carolina Botanical Garden is to:

  • Possess plant collections that do not harm natural areas and the native plant diversity of North Carolina and the Southeast
  • Protect and restore our Garden's highest quality natural areas by eradicating invasive exotic species
  • Interpret and promote the natural diversity of North Carolina and the Southeast
  • Promote the preservation of native biodiversity
Microstegium (bamboo grass)

Bamboo grass (Microstegium vimineum) is one of this region's
most invasive exotic plants. Photo by Johnny Randall

Definitions summary

  • Southeastern US Native:: An indigenous, regionally native taxon.
  • Exotic: Any taxon not indigenous to the southeastern US. The term exotic is synonymous with the terms non-native, alien, non-indigenous and introduced.
  • Invasive exotic: Any exotic species that threatens the survival or reproduction of native plants or animals or threatens to reduce biological diversity.

Native southeastern U.S. taxa

Organisms evolve in response to the physical, chemical, climatalogical and biological processes characteristic of a particular region. Native species are those taxa that occur in the region, or regions, where they evolved. (Within a region there may be local site adaptations that create ecotypes and other subspecific taxa.) The Nature Conservancy divides the continental United States into 63 ecological regions ("ecoregions"), based on climate and geology, rather than by artificial political boundaries.

Roughly eight ecoregions occur in the southeastern U. S. that are either partly or wholly in the states of Alabama, Arkansas, Delaware, the District of Columbia, Florida, Georgia, Kentucky, Louisiana, Mississippi, Maryland, North Carolina, Pennsylvania, South Carolina, Tennessee and Virginia. We consider any plant taxon that occurs within these ecoregions as native to the southeastern U.S., and those that occur outside of these boundaries as exotic.

We will determine which taxa are native to the southeastern U.S. based on the available floristic assessments of this region, that began in the early 1500s. Thus, native species are roughly those taxa that occurred in the Southeast at the time of European exploration. We will make determinations using the available literature, primarily the Synthesis of the North American Flora (Kartesz and Meacham, 1999) and other regional and local floras. Determinations of uncertain taxa will be made by consulting with the appropriate primary literature sources and/or individual systematists.

Exotic species versus invasive exotic species

According to the United States Department of the Interior (1997), exotic species (also called alien, introduced, non-native and non-indigenous species) are those taxa that occur "in a given place as a result of direct or indirect, deliberate or accidental actions by humans." Invasive exotic species are taxa outside of their native range that threaten the survival or reproduction of native plants or animals or threaten to reduce biological diversity.

It is sometimes difficult to draw a clear distinction between benign exotics and invasive exotics. Benign exotics include, for the most part, plant species that depend on humans for their survival (i.e., most cultivated plants). Invasive exotics, as aforementioned, threaten native plants because they can survive and reproduce without human intervention, and have become naturalized. A continuum exists between these two extremes and serves to complicate benign or invasive exotic determination. Moreover, a seemingly benign exotic species can become invasive if, for example, it begins to produce fruits that it did not previously form because a specific pollinator was absent (for example, strangler figs in south Florida). On the other hand, an invasive exotic species can become less invasive if it incurs a sufficient predator and/or pathogen load sufficient to limit its spread in natural areas (for example, Opuntia in Australia).

Existing collections and future plant accessions

The accession procedures for all plants, including exotics, are covered under the existing Plant Accession Policy and Procedures of 24 March, 1986. This Policy and Procedures does not, however, clearly address accession or removal of known or potentially invasive exotics.

Our policy, therefore, regarding known invasive exotics is that we shall remove invasive exotic species from existing collections and prevent accession of any exotic plant known to be invasive. Furthermore, we will only introduce plant species to cultivation that are native to the southeastern United States.

Some areas of the Garden traditionally contain exotic species, such as the Coker Arboretum, Garden of Flowering Plant Families and Herb Garden. In these areas we will continue to be judicious in selecting new plant material, will use native plants wherever possible, and will strive to promote native plant cultivars and select varieties. This will enable us to demonstrate to the public that spectacular native landscape material is available. (Appreciation for native biodiversity can also be gained by the public through interpretation of our Exotic Plant Policy and Procedures.)

For exotic plant accessions, where limited or incomplete information is available regarding invasiveness, we will use screening devices to identify the potential for invasiveness with a risk assessment scheme based on species' life history traits (currently in progress). We will create an invasive plant database from these data that will also include exotics already known or suspected to be invasive. This database will be made available to other botanical gardens and arboreta, the nursery industry, and to the general public.

Published on February 11, 2014 at 04:38:46 pm.

Grayscale Modular