Protecting the Environment Yard by Yard
A Conversation with Native Plant Advocate Carolyn Summers
A visit to Carolyn Summers’ native plant garden in the Catskill Mountains of New York is a reminder that we live on a planet that is paradise. A landscape architect, teacher, and the author of Designing Gardens with Flora of the American East, Summers has been a pioneer in the use of native plants, garden design and natural landscape restoration for more than 20 years. She created and maintains two demonstration gardens that show off plants that are indigenous to New York – one at her family’s suburban home and the other at what she has dubbed Flying Trillium Arboretum, a 300-acre private preserve in the southern Catskills.
We begin our tour of her experimental garden-arboretum looking out over a field filled with rare, blue flowering eastern lupine, Lupinus perennis. It would have been lovely to stay there for hours, watching the butterflies, bees and many species of birds flitting about. But we quickly moved to a rustic, handmade gate that led us in to the woods. Summers has been studying the evolution of two forest exclosures that she built to protect the woodlands from the overpopulating northeastern white-tailed deer. Inside the exclosures, native trees, planted as seedlings, now create a canopy that hovers over thriving understory plants, all essential for the survival of many species of wildlife.
Out another gate, we head to one of many native perennial borders. Each one is an exciting experiment in color, size and shape. The ideas behind all of this hard work are paying off, for both Summers and the wildlife that she so deeply cares about. "It really is true, if you plant them, they will come,” she says. “Wonderful creatures find native gardens."
Her enthusiasm is contagious. While working for the New York City Department of Environmental Protection, she developed the city’s “plant indigenous only” policy, which is still used today for construction projects there. After our tour of her demonstration garden, we sat down for a short interview.
Why and when did you begin working with native plants?
I started working with native plants in the 1980s, when I was studying to be a landscape architect at City College of New York. My whole purpose in becoming a landscape architect was to work with wildlife and to enhance wildlife habitat. It occurred to me that a lot of the human landscape that we use didn't have to be exclusively for humans, but that we could share this with wildlife.
Why is it important for people to plant native plants?
Regardless of where you live, every region and landscape has plants that are native, that are indigenous to it, that evolved in that same place. And because they evolved in a certain place and the wildlife evolved with them, they are all part of the same web of life. To introduce another plant from another region or continent – which we see a lot of – those plants can't interact with the ecosystem because they didn't evolve with, or have the co-dependencies, that native plants have.
What is an example of this natural co-dependency?
Since I read Doug Tallamy's book Bringing Nature Home, I've become really interested in caterpillars, and caterpillars are very, very picky eaters. They totally depend on native plants. In fact, if you don't have their particular plant, they won't come to your garden at all unless the butterfly happens to fly through for nectar. I could pick any number of millions of butterflies and moths whose interactions with plants are so interesting.
There is one particular butterfly, the Karner blue butterfly, Lyaeides melissa samuelsis, that is so picky it can only reproduce on eastern lupine. The eastern lupine is rare along with the butterfly itself, because people on the East Coast planted the showier western lupine, Lupinus polyphylus, and the western lupine is quite a bit more aggressive. It begins to take over at the expense of the eastern lupine to the point where now Maine is covered with the exotic lupine and the butterfly and the plant are both locally extinct in the state of Maine.
Here in New York we are lucky that we still have the Albany Pine Barrens, which is the last home in the state for the Karner blue butterfly and a substantial stand of the eastern lupine that the butterfly depends on.
How can backyard gardeners design gardens that will boost local and regional ecosystem resilience?
Most backyards have a lot of plants in them that aren't native, so those plants are essentially not functioning as part of the ecosystem. They might as well be plastic. The first thing to do is to identify the existing plants. Find out which plants are invasive, which ones are exotic and not invasive, and which ones are native. You can start by eliminating the ones that are a problem. This is especially important if you live near a park or a wildlife refuge, because exotic invasive plants spread and take over.
Next, identify the non-invasive exotics. You might want to leave some of those plants, because often they might form a large part of the look of the garden. When they die you can replant with natives. Some non-natives are just not attractive; those I would get rid of. Basically, take out what is invasive and unattractive and reintroduce beneficial native plants.
You can also remove some of the lawn area and replace that with native trees, shrubs, or herbaceous borders.
What are the benefits of native plants, in terms of creating habitat and managing water resources?
Some non-native plants were originally proposed for water control, but in fact because these plants tend to grow in monocultures, they wind up not being good for erosion control at all. The natural ecosystem of a prairie is one of the best examples of nature's sponges. The interlocking root systems of prairies hold the ground [together] because some roots go deep, some roots stay higher, some will spread out, and some will be tight and penetrating. The roots of a prairie work together, so there is no soil left untouched and those systems do not erode at all.
In a recent book, someone made the astonishing claim that Japanese knotweed is good for erosion control, but in fact it is not. People here in the Catskill Mountains are very upset about the Japanese knotweed, Polygonum cuspidatum, which has become invasive along trout streams. Because the roots of Japanese knotweed are so deep, the topsoil around that plant is actually eroding, leaving the banks of streams exposed to erosion. The knotweed blocks the ability of trees to grow and recolonize those sites to keep the brooks shaded. For survival, trout need clear running, shaded, cold streams, not sunny streams that are all muddied up.
Are native plants readily available to backyard gardeners?
If enough people request native plants, local nurseries will respond.
We have had some success here bugging our local nurseries for native plants. For now, the availability of the plants is a problem. The fact is that nurseries and garden designers continue to pump out the same old exotic and invasive plants, but with different colored flowers. So much of the energy and expense of modern day horticulture is spent on working with these exotic plants. This is a real problem. Also, it is not easy for homeowners to understand which plants are native and which are non-native. There are two websites that I would recommend for information about native plants: One, the USDA Plants Database and, two, the Ladybird Johnson Wildflower Center.
What most inspires you as you continue your work?
There is the beauty of the plants themselves, seeing them bloom and working with the endless combinations of colors and textures.
And then there is the feedback from observing the immediate response of nature to what I'm doing. Several years ago here in the Catskills, I planted Dutchman's pipe, Aristolochia tomentosa, the host plant for the pipevine swallowtail butterfly, Battus philenor. Soon after, I found pipevine swallowtail caterpillars all over that vine. That was the first recorded sighting of this butterfly in Sullivan County. It was the most exciting thing.
The enthusiasm and encouragement that I get from both my students and from people across the country that have read my book truly inspires me. All of this is a reminder of how important native plant gardening is, not only for wildlife but for humans too.