Restless natives

I am puzzled, confused and downright confounded. After more than 20 years in the horticulture business professing expertise in the region’s native flora, I thought for sure I knew the definition of a native plant. But after working on a project that has entailed conversations with botanists, nursery growers and conservationists (not to mention a certain amount of soul-searching), I’ve realized that there are varying opinions about what constitutes a native plant and how they should be grown in a nursery, promoted and used in the landscape.

Although I’m not in a position to resolve these issues, I can’t help but wonder what they mean to different gardeners, designers and other folks who patronize nurseries. Do you shop for native plants? Do you know which plants are native? And what definition do you use?

Defining “native” gets complicated; to a significant extent, it depends on your frame of reference and work with native plants. Generally, the term refers to plants that either have always existed or have evolved, unassisted by humans, in the area in question. This could be a state, region or even continent. People who use European settlement as a reference point believe native plants are those that existed in a specific location before Columbus’ arrival, European settlement and the introduction of European species. In this view, naturalized plants are those that were introduced by Europeans but have escaped from the garden and taken up residence in the natural landscape. Some field guides may call these plants native, but others don’t — even if they’ve been here for 200 years. And what about plants native to North Carolina whose seed was collected in another state — do they still qualify as natives?

Another issue involves cultivars: plants discovered and grown for some particular quality of performance or growth that’s considered an improvement over the original species. If we agree that the original plant is native to North Carolina, does that apply to the cultivar as well? What if the cultivar was originally found in northern Alabama? The answers depend on whether “native” refers to a specific geographic area. And the question of cultivars depends on the extent of one’s concern for the integrity of germ plasm (a plant’s reproductive cells). This may be important in restoration or reintroduction projects in which preserving the original germ plasm is critical.

Using native plants in the garden and landscape is an excellent idea. They provide food and shelter for native wildlife, insects and pollinators and give our gardens and landscapes a regional flavor. But native plants should be used only when the site’s soils and environmental conditions are appropriate and will sustain healthy growth.

My property, for instance, is on a north slope with rich soils and 75-year-old hardwood forests — a lovely location for native ferns, spring ephemerals (or short-lived flowers) and rhododendrons. But down the road at a new house site in the middle of a south-facing pasture, these same plants will struggle and probably fail if soil preparation and site conditions are ignored. The meadow and woods-edge plant palette, on the other hand, could provide ideas that might work well at that site.

What look are you aiming for? Can it be achieved in the landscape using only natives? If your location and tastes are conducive to this route, then go for it. But if you want to include both native and introduced plants to get the best color and performance, that’s OK, too. Just be sure that whatever you choose is well-behaved.

Sometimes you hear that native plants have adapted well to local conditions and can withstand insects, diseases and other environmental pressures. But when you remove forests, scrape off the topsoil and compact the remaining soils, the site has been so altered that only the toughest of plants will grow there — native or not. If you do select plants from a native-plant community found on a site with similar conditions — say a dry, south-facing exposure — you might be tempted to use mountain laurel, hickories or huckleberries. The latter two would be hard to find, as they’re among the many species that nurseries are still learning how to grow. Many factors are involved in using natives in our gardens and landscapes, and designers, gardeners and new homeowners with landscapes would do well to keep the issues in mind.

Before visiting your local nursery or retailer, consider whether you’ll want to know which plants are native to the mountains and which were nursery-grown rather than collected wild. Decide whether you want to know which plants are best for your site and if you’d be willing to pay a little extra for that information. Do you care if the plant has more leaf spot, or lesions, or a tendency to grow small? Or would you prefer a cultivar selected for better pest resistance or a stronger growth or flowering habit? But in that case, it wouldn’t be a native, would it? You tell me.

[Alison Arnold is horticulture director at The North Carolina Arboretum.]