Stories from the NFCCA Newsletter, the “Northwood News”

Northwood News ♦ April 2013

Going Native

What Makes a Plant ‘Native’?

By Jacquie Bokow

[This is the final part of a series on Bringing Nature Home:  How You Can Sustain Wildlife with Native Plants, a book on the vital importance of native plants to local ecosystems by Douglas W. Tallamy.  Part one appeared in the April 2011 issue.]

So, perhaps you’ve been convinced of the importance of having indigenous plants in your yard, but how do you tell which plants are not just native to the U.S., but native to our area?  You won’t get much help at nurseries where you buy plants.  Some may mark a plant as “native,” but that may only indicate it’s found somewhere in the U.S.  Some nurseries have a “native plant” section, but you should still check other sources before purchase.

The huge Chesapeake Bay Watershed stretches north into New York State.  Our area is part of the “Piedmont” Region.

How is “native” defined for plants?  Some people accept as native plants that have come from other countries but that have been in the U.S. long enough.  The broadest definition: a native is any plant that historically grew in North America.  Some people look at hardiness zones and figure anything that grows in a particular zone is native anywhere within that zone.

But Tallamy says that we must consider the roles plants play within their respective ecosystems, letting nature herself define what is native.  He writes:

“When a plant is transported to an area of the word that contains plants, animals, and diseases with which it has never before interacted, the coevoluntionary constraints that kept it in check at home are gone, as are the ecological links that made that plant a contributing member of its ecosystem.  In an ecological and evolutionary sense, the alien plant’s new neighbors won’t know what to make of it and, in most cases, will exclude it from their biological interactions.  The plant will occupy space and use resources (light, water, and soil nutrients) that would otherwise have been available for a native plant, but it will not pass the energy it harnesses from the sun up the food chain.  ...A plant can only function as a true ‘native’ while it is interacting with the community that historically helped shape it.”

According to Tallamy, “the Norway maple (Acer platanoides), an alien introduced into the ornamental trade from Europe, is now the most common shade tree in North America.  As with many ornamental species, it has escaped cultivation and is rapidly displacing native trees.”

If “native” and “alien” are “unambiguously defined by a plant’s evolutionary background,” then not only would plants from Europe and China be considered aliens, but plants from other parts of North America might also be called that.  Douglas firs (Pseudotsuga menziesii) are indigenous to the Rocky Mountains and Pacific Northwest.  If you plant one in our area, it would be thousands of miles from the community of organisms that were part of its evolutionary history.

“Douglas fir evolved in the Pacific Northwest of North America,” writes Tallamy, “where it performs important ecosystem functions.  Outside that regional habitat, however, it does not support diverse insect fauna and, therefore, does not supply as much food for other animals as it does in its native ecosystem.”

We have a blue spruce, native to western Colorado, in our yard; here, no bugs go near it.  It doesn’t contribute to the ecosystem in our yard.

Finding Native Plants

Our area is part of the Chesapeake Bay Watershed, which, surprisingly, extends all the way north to central New York State (see map above).  The U.S. Fish and Wildlife Service (FWS) classifies our area as “Piedmont,” with the “Coastal Plain” to the east and “Mountain” to the north and west.  (Also note that, due to global warming, our area has been reclassified from “Zone 6” to “Zone 7.”)

The U.S. Fish and Wildlife Service publication, Native Plants for Wildlife Habitat and Conservation Landscaping:  Chesapeake Bay Watershed, is a hugely useful resource for identifying all kinds of plants, ferns, shrubs, vines, and trees that are indigenous to our part of Maryland.  You can get a hard copy from FWS, see it online (see below), or search the listings on an online database.

Here are some sources you can check to find plants indigenous to the Piedmont Region:

Read Part 1 FWS Native Plant Guide [PDF] FWS Online Native Plant Database

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