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Wednesday - September 09, 2015

From: Big Sandy, TN
Region: Southeast
Topic: Seed and Plant Sources
Title: The Importance of Sourcing Local Genotypes
Answered by: Anne Van Nest


I would like to respond to the answer I got to my Mr. Smarty Plants question about native cultivars vs. straight species. 1) So if I, like many gardeners, don't have access to native plants with a local genotype I should just not bother planting any natives? This is what Bringing Nature Home is saying? 2) Almost all monarchs intermix their genes yearly in Mexico, so how can the adults not recognize "pollen"? (As far as I knew, the adults eat nectar, not pollen, of both native and non-native plants.) Think of the consequences of people fearing to plant natives that are not local genotypes!


Ideally the best situation would be to introduce additional native plants that are of the same local genotype so they would have the best chance to adapt and survive, as well as to service the indigenous insect and wildlife population. But, you are correct in saying that this is quite a challenge to source and accomplish. So, planting any form of native plants has many benefits and should be encouraged.

In Tennessee, there are several nurseries that specialize in native plants that perhaps you should contact to see where their seed or stock plants originated. These are listed on the Tennessee Native Plant Society website, Find Native Plants website, Wild Ones Tennessee Valley Chapter website, Plant Native website and the Gardening with Native Plants of Tennessee website. Once you have your list of potential nurseries, check them out on the suppliers section of the Lady Bird Johnson Wildflower Center website.

Here's some more information about the subject from the website: Understanding the Importance of Genetics

There has been a growing awareness recently of the importance of plant genetics in restoration projects. Genetic variation within plant species can influence their long-term chances of survival and growth. Sometimes specialized ecotypes within a species develop that are adapted to specific local environmental conditions. An ecotype is a certain population of plants within a species that, due to different genetics, has a different form (height, leaf size, etc.), flowering time, or hardiness that is adapted to certain environmental conditions. Plant ecotypes are not different species because they can still interbreed. Taking plant species that are of one ecotype and moving them to an area with environmental conditions different than the ones that the plant is adapted to, such as different freezing stresses or different moisture levels, can result in poor growth or death.

These types of genetic concerns have been recognized for quite a while in the forestry industry. Tree seed zones have been developed for specific tree species based on an understanding of their genetic variation across the landscape. Seeds are only planted in the same tree seed zone they were collected from, in order to increase the plants' chances of survival and adaptability. However, it is only recently that some scientists have begun to examine the genetic variation of herbaceous or shrub species across the landscape. Consequently there is very little information available yet about what might be the appropriate distance to relocate native plant species.

In addition to concerns about the ability of the planted species in restoration projects to survive and adapt, some people are concerned that the introduction of new genetic material in an area can damage local populations of native species. The thought is that new genetic material could result in the weakening of local populations' ability to survive and adapt to environmental pressures. This particular concern is still being debated. However it is clear that without a better understanding of the genetic variation of the species, it is a safer option to avoid as much as possible introducing non-adapted genetic material that may have unanticipated detrimental effects.

Depending on the genetics, there may be very different strategies for the appropriate places to collect propagation material for specific species. A general rule to follow is, if information is not available on the plant species' genetic variation, try to use local genetic sources for plant material whenever possible. There is no universal agreement as yet on the exact guidelines for "local" sources, however some factors to consider include whether the plant sources' genetic origin:

is in the same watershed
is in the same ecoregion
has similar soil type
has similar elevation
has similar slope
has similar aspect
has similar rainfall
has similar temperature patterns
has similar frost dates
has similar associated vegetation

Because this is a fairly new concern in the restoration field it may be difficult to get plants that are from as local a genetic source as you would like. However, a broad guideline to follow is to ensure that they are at least from the same ecoregion. There are a few different ecoregion classifications of the United States that have been developed. One popular classification is Bailey's ecoregions, a product of a cooperative effort of a number of different federal resource agencies and The Nature Conservancy. These regions are areas that have been defined as having similar natural communities, geology, and climate.

And to comment on the monarchs, The Xerces Society has started a Project Milkweed to return native milkweeds to American's landscapes. Milkweeds (Asclepias spp.) are the required host plants for caterpillars of the monarch butterfly (Danaus plexippus) and thus play a critical role in the monarch’s life cycle. The loss of milkweed plants in the monarch’s spring and summer breeding areas across the United States is believed to be a significant factor contributing to the reduced number of monarchs recorded in overwintering sites in California and Mexico. Agricultural intensification, development of rural lands, and the use of mowing and herbicides to control roadside vegetation have all reduced the abundance of milkweeds in the landscape. To help offset the loss of monarch breeding habitat, the North American Monarch Conservation Plan recommends the planting of regionally appropriate native milkweed species. However, a scarcity of milkweed seed in many regions of the United States has limited opportunities to include the plants in regional restoration efforts. Project Milkweed is producing new sources of milkweed seed in areas of the monarch's breeding range where seed has not been reliably available. Their website has a Native Milkweed Seed finder feature. In Tennessee the Plants for Pollinators, TN is featured with three species of milkweed available: Asclepias tuberosa, A. incarnata and A. syriaca.


From the Image Gallery

Common milkweed
Asclepias syriaca

Common milkweed
Asclepias syriaca

Common milkweed
Asclepias syriaca

Swamp milkweed
Asclepias incarnata

Swamp milkweed
Asclepias incarnata

Asclepias tuberosa

Asclepias tuberosa

Asclepias tuberosa

Asclepias tuberosa

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