What Counts as Native?

A Start on the Nitty Gritty

Jan 03, 2022

My friend Peggy is lucky enough to live near the Hummingbird Hill Native Plant Nursery in Charlottesville, VA. She shared with me the nursery’s winter 2021 newsletter, which included a quiz meant to prompt awareness of our natural surroundings. It’s a good thing the test isn’t graded, because after some early wins with “your name” and “today’s date,” my answer to just about every other question was ¯\_(ツ)_/¯.

I’ll share the full questionnaire in a future issue so you can be similarly humbled. Meanwhile, there was one prompt that has stuck with me: “Describe the landscape out your front door 20 years ago, 100 years ago, and 1,000 years ago.”

Ok, 20 years ago our front yard had a weeping Japanese cherry tree, some lawn and some shrubs. That’s easy, because we lived here then and I planted those hapless shrubs. One hundred years ago the landscape out our front door would have been farmland, possibly dedicated to tobacco.

One thousand years ago, though? The answer was not at all obvious to me. This immediate area is so densely developed that there’s no undisturbed land left as a reference. And to be honest, I had never stopped to wonder.

But that’s precisely what we need to figure out if we want to be responsible stewards of our outdoor spaces: what was the ecosystem before humans intervened and replaced the native species with crops, turfgrass lawns and exotic ornamental species? Not because we need to replicate the 1000-year-old ecosystem plant-for-plant, but because that context should inform our gardening choices.

What Is a Native Plant?

A native plant is one that has evolved over hundreds or thousands of years in a particular region or ecosystem. Native plants and animals that have evolved together often depend on one another for survival and reproduction. Remember: those native plants and animals that depend on one another also provide the ecosystem functions that allow us humans to survive.

Only plants found in this country before European settlement are considered native to the United States. In addition, the word “native” should always be used with a geographic qualifier, as in, “native to southern coastal Connecticut.” If you go to your mainstream garden center and see a table or a section marked “native plants,” what that often means is “native to the whole US of A.” But a saguaro cactus – at home though it may be in the Sonoran Desert of Arizona – just won’t cut it in Lempster, New Hampshire.

Saguaro National Park, Arizona. Credit: Jeff Hollett

So if someone tells you a plant is native, ask, “to where?”

A non-native plant is one that evolved in another part of the world and was introduced to a new place with human help, either intentionally or accidentally.

An invasive plant is a non-native species that evolved in another part of the world and is capable of spreading rapidly, causing ecological or economic harm, or threatening human health. Note that not all non-natives are invasive. However, it’s not always possible to tell upfront which non-native plants might develop invasive qualities over time.

Unfortunately, many – if not most – of the plants available in U.S. nurseries and big box stores are non-native. These plants disrupt the food web and some of them also become invasive, outcompeting native species and degrading habitat.

The bottom line is this: your gardening choices have a tangible impact on the health of our surrounding environment and the quality of our lives. Choose with intention.

How to Figure Out What’s Native Where You Live

First, native plants scoff at your hardiness zone maps. Forget about them. Think instead in terms of what your ecoregion is. Ecoregions are areas where ecosystems are generally similar, taking into account geology, land forms, soils, vegetation, climate, land use, wildlife and hydrology. You can find your ecoregion here.

US EPA Level III Ecoregions of the Continental United States

If possible, you want to be planting seeds or plants that are indigenous to – and that were propagated in – your own ecoregion.

Bethesda, MD is in the Northern Piedmont region. Counterintuitively, this means my yard may have more in common with a property in Newark, NJ (a three- to four-hour drive away) than one on Capitol Hill in next-door DC, because most of Washington is in the Southeastern Plains region, while northeastern Jersey’s at the tippy-top of the Northern Piedmont wedge.

Another way to think about it: red maples have a huge native range, from southern Newfoundland to Florida and from the Atlantic coast to Texas. But there will be genetic variations and adaptations within the species, so a seedling propagated in the suburbs of Minneapolis may struggle in the suburbs of Atlanta, and vice versa. (Some of us humans can probably relate.) The more you can source your seeds and plants from within or near your ecoregion, the better.

When you get down to deciding what to actually plant, I’m told the best approach is to visit wild areas in your ecoregion to see what’s growing there naturally and to emulate. That’s not entirely practical, though, because a) where are we supposed to find those wild areas, anyway? and b) even if we find them, how will we know what the heck we’re looking at?

As a shortcut, I recommend starting with the National Wildlife Federation’s Native Plant Finder. This very cool site will tell you not only what is native in your zip code, but it will rank flowers, grasses, trees and shrubs by their value to the ecosystem. So in my zip, for example, a goldenrod will support 118 species of butterflies and moths. Compare this to lily-of-the-valley, which will support only one. That makes goldenrod a keystone species. The more keystones I plant, the more I’ll be helping not only insects, but also the little critters that eat insects and the bigger critters that eat the little critters.

If you want to reverse the lens and determine whether a plant you already know and love is native to your neck of the woods, I recommend the Missouri Botanical Garden’s Plant Finder, which will usually tell you a plant’s home territory. If it says “Native Range: Japan, China, Korea,” or worse, you get a prompt in red saying, “Where is this species invasive in the US?” then you know you’re barking up the wrong tree. If you’re pretty sure your beloved species is native to the US but want to know more, the Lady Bird Johnson Wildlife Center Plant Finder is a good bet. You plug in the name of the plant and you’ll get all kinds of information about its characteristics, growing requirements, and geographic distribution by state. But remember, most states contain multiple ecoregions. Just because something thrives in Sacramento doesn’t mean it’ll be sweet on San Diego, too.

If you want to dig even deeper, there’s a geeky site called the Biota of North America Program (BONAP) Taxonomic Data Center. You plug in the Latin genus and species of a plant (find those on the Lady Bird Johnson Wildlife Center site or Google if you don’t already know them) and BONAP will show you on a county-by-county basis whether that plant is native.

Biota of North America Program County Distribution Map for *Pinus taeda*

For no particular reason, I’m fond of the loblolly pine. The BONAP map above shows its range, with brown meaning “not present,” dark green meaning “native,” lime green meaning “native and not rare,” and yellow meaning “rare.” I don’t find the BONAP map color key very intuitive, but my understanding is that loblolly pines will do best in the lime green counties.

Finally, you can count on your local native plant society (as recommended here) to be a font of useful information, including plant lists.

A Thousand Years Ago

I’ve still got due diligence to do on my local natural history. But from what I’ve learned to date, the spot where our home sits was once an oak-hickory forest. Before European settlers arrived, it would have included oaks and hickories, of course, but also red maples, ashes, birches, beeches, black cherries, tulip trees, hemlocks and pines. Various species of viburnums, rhododendrons, serviceberries, witch hazels, flowering dogwoods and mountain laurels would have made up the understory. The ground layer would have included Solomon’s seals, mayflowers, mayapples and some ferns. It’s unlikely this suburb will revert to a forest in my lifetime. But every time my neighbors and I plant one of the species from this plant community, we’ll be rebuilding a healthy foundation for the ecosystem functions that support us.

PS. I’m aware that my references are all US-centric, since that’s what I know so far. Some of you fine readers live beyond these shores, though. I hope the underlying principles are still relevant. Meanwhile, if you have non-US references, links or observations to share, please do so in the comments. I’d love to broaden the perspective!

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