Native Plant Society of Oregon
****3/15/00 *****ROUGH DRAFT****BRUCE NEWHOUSE
Policy on Use of Local Native Plants for Gardening, Landscaping and Restoration
Purpose: To provide a definition of "native plants" and related terms, and provide guidance to landowners, nurseries, governmental agencies and other organizations regarding the use of native plants for landscaping and restoration.
There is great interest, and at the same time, confusion, about the definition and use of "native" plants for landscaping. What does "native" mean, and what is the purpose of planting "native" species?
Every ecoregion on the planet has its own, unique natural heritage: a local species assemblage which evolved there that is found nowhere else. Each one is a product of the interaction of geology and soils, climate, wildlife interactions, natural disturbance (e.g., flooding), and many other factors over time. The plant communities that comprised Oregon's flora before EuroAmerican settlement evolved over a period of thousands of years. Plants co-evolved with animals, fungi and other organisms and innumerable interrelationships exist - typical of any ecosystem. The biodiversity of each unique ecoregion, once lost, is not possible to recreate.
This uniqueness and diversity already has been lost in many areas in Oregon. For example, there are no surviving remnants of upland prairie communities in the Willamette Valley - although they were common at the time of EuroAmerican settlement. They are extinct, and we will never know exactly which plant species and communities comprised this habitat type. Wet prairie and oak savanna habitats are extremely rare as well, but we still have representative examples which provide us with an idea of what these communities might have looked like. Other ecoregions in Oregon also have drastically changed in the last 150 years because of land conversion to agriculture, rural housing and urban uses, and because of significant impacts from introduction of non-native species, resource extraction, fire suppression and other causes.
Ecological values and relationships are unique within each ecoregion, and do not occur with regard to a political boundary such as "Oregon" or the "Pacific Northwest." For example, if a certain species of plant provides a larval host for a certain species of butterfly, that plant has an additional, local ecological value that we can recognize. If we plant that same species in another ecoregion where it is not native, and the butterfly species is not native there either, that additional value does not exist. A species introduced from a neighboring ecoregion may not have any more ecological value locally than a species introduced from another continent.
Each locally native species has evolved differently from other populations of the same species in other areas. Biochemical composition and morphology (physical appearance) are unique between different populations of the same species in different regions. This is one form of biodiversity: that which occurs within a species. Importing the same species from a distant region (a different "genotype") can cause the mixing of genes, the loss of biodiversity, and possibly the loss of a species' local adaptation to local conditions. The following statement is from the Society of Ecological Restoration web site:
The Society for Ecological Restoration advocates the planting of regional ecotypes at restoration project sites to assure fitness of the planting stock and to preserve genetic integrity in local species populations, especially for species verging upon local extirpation. The procurement of suitable planting stocks should not jeopardize existing populations of rare taxa.
In many cases, it may be more benign to plant a non-native, non-invasive ornamental than to plant a native species with a genetic makeup that could affect unique, local genetics of a plant. These local genotypes account for different features in a species such as a unique, local flower color, or a nectar composition uniquely suited to a certain local native species of butterfly). Genetic makeup also determines a local species' adaptability to local site conditions. Because local native species evolved with local native soils and climate, they are adapted to living without irrigation, fertilizer and pesticide use. (These factors are rapidly becoming increasingly important because of our understanding of negative impacts they cause on native salmonids in local rivers, and because of federal regulations currently being developed to address these impacts.)
This is a relatively new area of concern to ecologists, and little is known about potential impacts. Therefore, it is prudent to minimize mixing of different genotypes by selecting plant stock that is propagated from stock as locally as possible, and preferably within the same ecoregion.
II. Benefits of Local Native Plants
When planning landscaping or restoration projects, the ecological values of using locally native species rather than non-natives (species which are native someplace, but not locally native) are numerous. The primary goal of using locally-native versus using introduced species is to help perpetuate native species and protect and restore the integrity of native ecosystems.
Gardening, landscaping and restoring with locally propagated native species insures that:
local plants, and the animals, fungi and other organisms that depend on them, will continue to have habitat
non-native, invasive species are not being introduced
plants are adapted to local soil and climate conditions
unique genetic makeup of local plant populations will not be polluted by genes from other regions
NPSO encourages local chapters, as well as federal, state and local government agencies and private organizations to form partnerships to research local native plant communities within their ecoregion, and develop local native species lists.
Because of the many benefits provided by natives, and the potential issues with altering the genetic makeup of locally-native species, NPSO strongly recommends the following guidelines for use in selecting native plants. We recommend these policies for the home landscaper, the restoration project manager, and very importantly, for nurseries.
NPSO has adopted these priorities for use in selection of native plants for gardening, landscaping, restoration and nursery propagation:
1. First priority: select locally-native species propagated from stock within a 10 mile radius within the same ecoregion. Select plants suitable for the conditions of each site -- if possible, select species that occur in the plant community(ies) native to the site. (Many species may not be available in local nurseries; they may have to be propagated directly from local native stock with help of a botanist. Follow NPSO collection guidelines.)
2. Second priority: select locally-native species propagated from stock beyond a 10 mile radius within the same ecoregion.
3. Third priority: select species not native locally, but native to an adjacent ecoregion.
4. Fourth priority: select species not native locally, or in an adjacent ecosystem.
5. Lowest priority: select locally-native species propagated from stock not locally-native (i.e., from an adjacent ecoregion or farther away).