by Scott LaFleur and Tom Smarr
A sustainable landscape preserves and protects nature’s balance. To develop a sustainable landscape requires a well-planned design that addresses all aspects of environmental processes. All facets that involve the livability of a community such as energy, materials, buildings, water, air, and site must be incorporated into a holistic planning approach. Plants are an integral part of the sustainable landscape as long as the species used are well-suited to the existing light, moisture, and soil conditions. Such plant choices require low input of labor, fertilizers, herbicides, insecticides, and fungicides to thrive.
We feel strongly that a successful sustainable landscape incorporates native plants into the design. “Native” is broadly defined as a plant having occurred before European settlement in North America. To gain full sustainable benefit of using natives in the landscape one should choose plants found regionally. There are many distinct habitats and climatic environments found throughout the country. By understanding the endemic plants in these communities, we can better understand how best to place them in the different growing conditions of designed landscapes. Some species will tolerate a range of landscape condition possibilities while others are more specific. In New England, we enjoy the adaptability of the native highbush blueberry shrub (Vaccinium corymbosum) that grows in wetland-like conditions, but will also tolerate average garden soils. One can also choose the lowbush blueberry (Vaccinium angustifolium) for mountainous or drier conditions. American witch hazel (Hamamelis virginiana) is a champion of versatility, growing well from wet to semi-dry, sunny to half-shade.
Native plants are essential to sustainable landscapes, but need not be exclusively used. Plants that are exotic, or not native to a local region may fill a need (such as food crops), but often offer nothing in the way of food or habitat for key wildlife species. Any plants chosen for a specific site need to be evaluated for overall impact on the immediate and surrounding landscape. Although a plant may perform wonderfully in a specific garden, it may seed excessively or spread vegetatively and cause havoc in surrounding gardens and natural areas. The actions taken to battle the spread of invasive plants cost billions of dollars in resources and labor, and result in the loss of economically-valuable native plants. By limiting biodiversity and creating dysfunction in ecosystems, invasive plants cause even greater ecological losses.
The choice of native plants has an immediate positive impact on the environment and embraces the regional cultural identity that has been so readily lost in conventional garden design. Large suburban neighborhoods displace healthy native habitats with vast stretches of lawn, dotted with a handful of plants that are heavily dependent on water, fertilizer, chemicals, and gasoline for machine-based maintenance. This is not a sustainable practice. Creating “regional style” landscapes can foster a diversity of habitats for plants, animals, and human experiences. Not only are these “local” plants pre-adapted to grow without high inputs of energy, they also are part of the local food web and provide nectar for insects, shelter for birds, and food for wildlife. Thus, growing native plants enhances the existing local biodiversity. By being sustainable design we participate in the conservation of flora and fauna of our region.
Over the past couple of years we have been working with entomology enthusiasts in our area to raise endangered native Baltimore Checkerspot Butterflies. Although these voracious caterpillars damage our white turtlehead plants (Chelone glabra), they recover after the beautiful butterflies emerge. In return for temporary blemishes to a handful of plants, we get to enjoy the full breadth of our natural wonders. The Baltimore Checkerspot is adapted to feed on the moisture-loving turtlehead and arrow wood (Viburnum dentatum), whose toxins help protect them from predation. Draining every wet piece of land for building is an obvious threat to species survival. Replanting those areas with gardens lacking native plants is a more subtle threat. So often, the loss of just one species causes a cascade of species losses. Simply leaving the soil unchanged and selecting native plants appropriate to that spot avoids the losses and brings huge benefits. For so many, it’s the wildlife that shares our back yards that make a house a home.
The choice to design a sustainable landscape in our own yards does not mean we must have a wild and untamed landscape. Native plant species, when planted, sited, and maintained properly, have a stately and refined appearance. In fact, you may already be gardening with some native species. There is nothing more refined than a nicely clipped hedge of American holly (Ilex opaca), a driveway alleé’ of sourwood (Oxydendron arboreum), or the addition of white foamy flowering spurge (Euphorbia corollata) to the cottage perennial border. Clumps of blazing stars (Liatris spp.) brighten many mailbox plantings in our very suburban location, and are well-suited to the hot and dry roadside. Some of the stateliest shade trees species such our native oaks and maples range widely across the country, each with their own unique and interesting features of growth, branching habits, and seasonal color.
Color need not be compromised when you choose native plants. People are amazed when they discover that wild pinks (Spigelia marilandica) are a northeastern native, astonished by the powerful color of purple love grass (Eragrostis spectablis), often dismissed as a roadside weed, and mystified by the four-sided, egg-shaped fruits of the silverbell tree (Halesia tetraptera). Cultivars can also be fun, providing many choices in foliage and flowers. Foam flower (Tiarella ‘Black Snow Flake’) has intricate dark variegated leaves and Carolina spice bush (Calycanthus ‘Athens’) has apple-green flowers and an amazing strong apple fragrance. Both are as refined as any exotic selection.
Other benefits can also be achieved by using native flora. By reducing lawn with a mosaic of groundcovers, grass-like sedges, native short fescues, or other perennial favorites, an immense amount of energy is conserved. We should select plants that have root forms which hold soil and prevent erosion. Garden spaces can be more efficient at capturing rain water and preventing runoff. Turn problem sites into designing opportunities by transforming low wet spots into rain gardens or dry hot spots into arid/rock gardens. Minimizing soil disturbance during construction will allow the local soil life web to remain healthy and enables proper nutrient cycling that is essential for the prosperity of plants. Constant use of fertilizers and pesticides creates a sterile soil, devoid of the microbes upon which all plants rely for survival. Thus a completely service-dependent and non-sustainable landscape is created. Try organic care and composting instead.
The hand that we extend in creating sustainable landscapes right outside our doors will create that connection with the living environment which is so quickly being lost to the virtual reality that our urban and suburban lives have become. Although we cannot solve all of the environmental damage being done, we do have the power to make holistic decisions in our landscape that are ecologically responsible. Selecting regional plants will keep the unique character of your particular cultural place alive and vibrant, as well as answering the needs of local wildlife. Encouraging diversity will promote a balanced and healthy environment for us and our wildlife neighbors. Preserving healthy soil maintains natural protections against pests and diseases. All this can be done while never compromising on the style, mood, and feeling we are trying to convey in our garden. To sustain ourselves we must sustain our habitats. To sustain our habitats we must work within the environment and live to become a part of the ecosystem, not an impediment.
About the Authors
Scott LaFleur, Senior Horticulturist, and Tom Smarr, Director of Horticulture, are at Garden in the Woods, the Botanic Garden of the New England Wild Flower Society. You can find out more about native plant horticulture at www.newfs.org.
Columbine and Witchhazel photos by Jennifer Chesworth
All other photos from Wikimedia Commons
(This article originally appeared in ELA’s newsletter The Ecological Landscaper in Winter 2006-07)