Consider the Source
E. Storey
Consider the Source Preserving something special from Minnesota’s natural history
The Minnesota Department of Natural Resources estimates that only traces – less than one percent – of native plant communities remain in a state that was once abundant with prairie and oak savanna. In the urban landscape, we may try to preserve a piece of natural history when we garden with Minnesota native plants. It’s important, however, to make sure that plants making this claim are truly native to Minnesota.
What is native? Since all plants are native to somewhere, definitions are somewhat arbitrary. But what is usually meant by "native" in landscape or restoration work are those species discovered growing in a particular area at the time of European settlement. Because some of the main benefits of using natives rely on their adaptation to conditions in a particular area, the seed source should be considered. Plants of the same species grow over a wide geographical area and sub-populations adapted to differences in growing conditions and thus local "ecotypes" evolved.
For example, seeds from a little bluestem (Schizachyrium scoparium) prairie grass plant that grew in our area of Minnesota will contain genetic material which produces plants that are better adapted to our shorter growing seasons and colder winters than seed from a little bluestem grown in Kansas. While strict determination is unrealistic and ignores the natural moving of material with insects, birds, and land animals, likely determinants for selection in most plant populations are annual precipitation, season length, and altitude. Plants also support other organisms that have co-evolved with them, including pollinators, insects, birds, mammals and other wildlife that use the plants for food and shelter. Restoring native plants to areas where they are well-suited increases the chances of planting success, helps preserve organisms that are dependent on them, and it helps preserve the genetic diversity of the plants.
Shop locally When Minnesotans use a non-local source of native plants, for instance Canada milk vetch (Astragulus canadensis) shipped here or grown from seed from another state, these plants have the potential of diluting or contaminating the local population. There may also be important genetic differences within native populations that we do not yet know about. With the news full of stories about the commercial value of native plants, it seems more important that ever to preserve local populations since a possibility exists that the next medical breakthrough could come from a native plant.
The most commonly accepted definition for local ecotype is a seed source that originated within 200 miles of a given project's location. The best way to assure that the type is still "true" is to get it from a supplier that raised it within that range. A list of local suppliers who honor this use of local ecotype can be found through the Minnesota Department of Natural Resources: http://www.dnr.state.mn.us/gardens/nativeplants/suppliers.html.
Partners in encouraging diversity While many Blue Thumb Partners (www.bluethumb.org) support and fund the use of non-native landscape plants, it is a collective goal that Blue Thumb projects using native plants require plant material propagated from sources no further than 200 miles away. Without diverse species of local ecotypes, our vegetated areas will be more homogenous and less diverse -- like so much of the landscape.
Grey box Ecotypes: Plants of the same species that have adapted to slightly different environmental conditions of their location.
Posted: August 7, 2007