What better day than July 4th – our national independence day – to consider the issues surrounding gardening with natives versus gardening with plants of foreign origin? (For the record, I grow both.)
And what, for that matter, is a truly native plant?
Typically, we define “native” in terms of national geographical boundaries – that is, if a plant is indigenous within the confines of the United States, we define it as an American native. Or we may define it in terms of continental land masses, as in the case of a “North American native.” This distinction can help us avoid introducing exotic and invasive plants into our home terrain, but it is at best a blunt instrument.
I was reminded of this recently by Dr. Daniel Duran of Drexel University in a talk he gave at the Millersville (Pennsylvania) Native Plants in the Landscape Conference. Duran distinguished between natives of such a political/geographical kind and those plant types that are genuinely indigenous to your local ecoregion. These more narrowly defined natives are typically adapted to the local conditions. Introducing specimens of the same species from outside the ecoregion and allowing them to interbreed with their indigenous fellows is likely to create offspring that are less well adapted to local conditions, plants that aren’t native in the strictest sense.
This makes a good case for patronizing, whenever possible, local Mom-and-Pop nurseries that propagate their own plants rather than other retailers that import them from out-of-state wholesalers. Local native plants societies can help you in your search for such growers. At the very least, when shopping for natives, one ought to shop at specialist native plants growers that have some idea of the provenance of their plants and can discuss such issues with you knowledgeably.
Despite your best efforts, you may be unable to find such local sources for the plants you seek. If so, you can take comfort in the thought that plants native in the broader sense – plants native to other ecoregions within North America, for example – will at least not introduce invasives, and may well prove well-adapted. But, at least from an ecological perspective, local is better.