C. Colston Burrell: Gardening for Beauty and Ecology

Although Charlottesville and its surrounds proudly claim Cole Burrell as a local talent, he truly is known the world-over. He is an acclaimed lecturer, garden designer, photographer, and writer. The author of 12 gardening books, Cole has twice won the American Horticulture Society Book Award. He has been at the forefront of gardening with native plants from the very start of his career in the 1970s. Included on the list of his publications are A Gardener’s Encyclopedia of Wildflowers (1997) and Native Alternatives to Invasive Plants (2006). Cole is principal of Native Landscape Design and Restoration and leads garden tours in the U.S. and abroad through Garden and Nature Tours with C. Colston Burrell. Many of us have had the opportunity to tour his 10-acre Albemarle County garden, Bird Hill. The garden is a magical demonstration of his lifelong devotion to landscape design that pairs beauty with ecological benefit. This interview is of compelling interest at a time when so many gardeners are learning about the benefits of using native plants and designing home gardens as home ecosystems.

YOU HAVE BEEN STUDYING AND WORKING WITH NATIVE PLANTS THROUGHOUT YOUR CAREER. IN FACT, YOU WERE A FOUNDING MEMBER OF THE VIRGINIA NATIVE PLANT SOCIETY. WHAT ARE SOME OF THE CHANGES YOU’VE SEEN?

The definition of native has changed over the last 40 years. You can talk about a plant being native to the East, West, or Midwest. A plant can be native to your state or your county. In fact, some believe a plant should be from no more than 50 miles down the road. The definition of native is complex, and I think it also depends on what we’re trying to achieve. The distribution of some native plants is huge, covering an area east of the Rockies. Others are restricted to very specific conditions in just a few localities. As climate warmed and glaciers retreated further north about 4,000-6,000 years ago, plants moved back to northern regions and plant communities reestablished themselves, so that what we define as native today is new in geologic time. A more recent definition of native recognizes that native plants don’t occur in a vacuum; they have a context within an ecosystem. We can use Virginia sweetspire (Itea virginica) as an example. It is native to only one of the four major bioregions in Virginia. It is not native to the Piedmont region, but it is a beautiful and useful landscape plant. In the wild, Itea grows in swamps and other wetland environments, and is mostly restricted to the coastal plain. If we think of the narrowest definition of gardening with native plants, we would be mindful of this niche environment when we plant Itea. But most of us define native more broadly as we choose plants for our gardens here in the Piedmont.

IS IT HELPFUL TO LABEL NURSERY PLANTS AS “NATIVE TO VIRGINIA”?

I applaud the effort to introduce more gardeners to the idea of gardening with natives, and to make this easier for them to do. Let’s be aware, however, that some native plants, as described above, are native throughout an area as big as Eastern North America while others, such as Itea, are native only to a particular ecological niche. When we define a plant as a Virginia native, I believe the seed source or cutting source should be from Virginia. If not, perhaps it might be more useful information if we say it is a North American native or an Eastern U.S. native.

TELL US HOW YOU’VE USED NATIVE PLANTS IN YOUR GARDEN, BIRD HILL

One of my projects during Covid was to replace my 3-acre plastic deer fence around my house with a 10-foot metal fence around the entire property. I now get to see many of my plants uneaten by deer and in bloom for the first time! I have been planting thousands of native plants in meadows and woods. When sourcing the plants, I try to stick as close to home as possible. I’ve used the Flora of Virginia app as my source of identifying native ranges and soil preferences. I haven’t counted out the numbers yet exactly, but of the 90 native species I’ve added, about 30 are local to Albemarle County.  I have made exceptions for several showy genera that are favorites, including Trillium, Phacelia, and Kentucky lady’s slipper (Cypripedium kentuckiense) that are native farther afield.

ALTHOUGH YOU WERE ONE OF THE EARLY LANDSCAPE DESIGNERS IN THE NATIVE PLANT MOVEMENT, YOU ARE KNOWN ALSO FOR INCLUDING NONNATIVES IN YOUR GARDENS. HOW DID THIS COME ABOUT?

I am a firm believer and proponent of using native plants. They are beautiful and they give a sense of regional character and identity that makes my Virginia garden unique. I have always been interested in the coevolution of plants, insects, birds, and other living things. This coevolution is dependent on the inclusion of native trees, shrubs, and herbaceous plants that are highlighted as “keystone” plants, a term that is now familiar to many through the work of Doug Tallamy. Nonnative plants can also be used to achieve different goals, both aesthetically and functionally. There are so many wonderful plants grown across the globe, and these nonnatives will thrive in our gardens when conditions are like their original environment. Many of these plants appear earlier in spring than our natives, and some bloom later, extending the bloom season and making pollen and nectar available to insects when there are no native flowers available.

 

Let me give you an example from my previous garden in Minnesota. I started my garden in late summer, and that autumn was very mild. I had done lots of soil amending and, as a result, some plants were spurred into unexpected growth. Nonnative ‘Mary Stoker’ chrysanthemums bloomed profusely in November and were covered by bees that were looking for nectar due to the unseasonably warm weather. This showed me that nectar and pollen can come from many different sources, including nonnative plants. This garden was 1/8 of an acre and I planted over 600 species of plants. If I had limited myself to using plants native to this flyway along the Mississippi, I would have had 40 species. The diversity of plant life attracted a huge number of pollinators and 172 species of birds.

WHAT DO YOU THINK OF THE USE OF CULTIVARS?

Every garden is a novel ecosystem, with a novel plant community created or modified by humans. How we choose to structure and populate that garden is what makes it our own and gives us joy. Many believe that you should never plant cultivars. Again, you must consider your goals and balance aesthetics with ecology. If you are simply putting a name on a plant found in the wild, it is still a “straight species” even though it has a name attached to it. Some cultivars have been demonstrated through research to be superior to the species tested as far as nectar or pollen production. Often selections are made to preserve a unique flower color, but may also relate to a distinctive leaf or fruit color variant. Any of these variants may alter the perception of a nectaring pollinator, a caterpillar feeding on the foliage, or a bird consuming a fruit. Tallamy’s research demonstrated decreased insect grazing on colored foliage. Sometimes the converse is true. Research with phlox cultivars found that nonhybridized cultivars of Phlox paniculata were more attractive to pollinators than were the species. Hybrid cultivars are a different story, and consider your goals when choosing to use them.

WHAT IS THE DIFFERENCE BETWEEN AN INVASIVE PLANT AND A PLANT THAT IS AGGRESSIVE?

Many people consider any plant invasive if it performs too well. Monarda  (M. didyma and M. fistulosa) is a good example. When we make a garden, we often prepare the garden soil and provide perfect growing conditions to give our plants a good start. Monarda is stoloniferous and responds by growing aggressively, often outcompeting less vigorous companions, which makes us unhappy. Monarda doesn’t escape its garden boundaries, however, and cause harm. An invasive plant is generally not native to a region or country, escapes cultivation, and causes ecological harm by outcompeting native species in the wild. This is very different from a plant that grows profusely in cultivation. Some invasives, such as Callery pear, come from horticulture, and others, such as stilt grass and garlic mustard, come from other sources.

WHEN WE INCLUDE NONNATIVES IN OUR GARDENS, HOW DO WE PROTECT AGAINST PLANTS SHOWING INVASIVE CHARACTERISTICS, THAT IS JUMPING THE LINE AND CAUSING HARM?

This can be difficult to predict. Some invasive plants escape and establish readily, while others take years to show up. If a plant is a prolific self-sower and begins to show up on the fringes of the garden, it may become invasive.

WHAT ADVICE DO YOU HAVE FOR ESTABLISHING DENSE PLANTINGS IN LESS-ESTABLISHED GARDENS?

Plant “lot line to lot line.” If you have existing native vegetation, leave it and work in front or around it. Use the biology of plants when composing combinations—bulbs fit in neatly with plants that have deep tap roots and fibrous roots. Work with layering to form dense vegetation that will keep out the weeds and invasives. You could plant annuals the first year, such as zinnias or something for nectar/pollen balance. Plant low-growing, spreading perennials such as green-and-gold (Chrysogonum virginianum), pussytoes (Antennaria plantaginifolia and A. neglecta), and snow flurry white heath aster (Symphyotrichum ericoides var. prostratum ‘Snow Flurry’). Spread a seed packet of alyssum, or a cover crop such as alsike clover (Trifolium hybridum) or buckwheat. Underplant a woodland garden with blue phlox (Phlox divaricata).

 

WHAT DO YOU MEAN BY VERTICAL INTEGRATION AND HORIZONTAL INTEGRATION?

Every plant community, forest, or meadow has a recognizable structure which creates layers. In a woodland setting, provide structural diversity with trees at different heights and shrubs that provide a layer beneath the canopy. Trees and shrubs of different densities and forms also contribute to diversity. For example, if you clip a hedge so that it is very dense, the density will help birds avoid predators. It has been well documented that 5 species of arboreal warblers (MacArthur’s warblers) each utilize a different area at a different height within the same tree (spruce, fir, and pine) for feeding. Overall, the study concluded that “the birds behave in such a way as to be exposed to different kinds of food.” In addition to this vertical layering, plants are distributed in horizontal patterns created by differences in growth habit, soil, and moisture. You easily see these patterns as you gaze across a meadow. In a woodland, they are less obvious, but thickets of shrubs, glades filled with ferns, and sweeps of Virginia bluebells on a floodplain, are good examples.

 

YOU EMPHASIZE THE NEED FOR GARDENERS TO BE AMATEUR ECOLOGISTS. WHAT SHOULD I LOOK FOR WHEN SURVEYING MY YARD?

The saying, “Plant it and they will come,” is actually true. As we’ve discussed, the garden structure should include keystone tree species such as oak, cherry, maple, and shrubs such as blueberry, rose, and viburnum. But insects will use nonnative trees as well. Look at the genus of the keystone plants. For example, a nonnative cherry will make a greater contribution than a nonnative ginkgo. But if you love a ginkgo for aesthetic reasons, include it. Gardens are about both ecology and beauty.

ANY LAST WORDS FOR OUR READERS?

Gardens should be both functional and aesthetically pleasing. They are also a lot of work! No one will want to put in all that work of creating and maintaining plantings unless the garden is a place of beauty. Start small and set achievable goals. It is easier to move the goalpost forward than to never make it to the post. When I think people feel discouraged or guilty about their plant choices and don’t want to keep trying, it makes me sad. Don’t be discouraged! Plant for joy. Try different things. I have a banana tree in my garden! (Cole’s garden also famously has a blue-painted tree.) It’s YOUR garden to enjoy.

 

Feature Photo: Bird Hill’s Blue Tree by C. Colston Burrell