Paved driveways and sterile lawns replace native oaks, pine, holly, mayapple and spring beauty. Our garden centers market highly invasive species like Bradford pear, nandina and Russian olive which not only homogenize our lawns but overrun surrounding areas supplanting pockets of native landscape that have managed to avoid the bulldozer.
A typical suburban landscaping
This is the story of towns and neighborhoods throughout the United States. We have replaced species rich forests and grasslands with great rapidity through intensive agriculture and urban sprawl resulting in loss, reduction, fragmentation and degradation of plant and wildlife habitat.
Native plants and local wildlife diversity
Local wildlife diversity and native plants evolved and exist in an inextricable relationship. For many of our insects and birds, native plants are the major source of food and nesting sites without which their population will decline. And without wildlife to disperse seeds, many native plants would also decline.
A bumblebee feeding on a bee balm (Monarda fistulosa)
Studies show that a predominance of non-native plants in many cases cause a decline in wildlife populations by changing structure and composition of vegetation as well as reduction in food, cover and optimal nesting sites (1, 2, 3). Fruits of some non-natives can even poison local wildlife—nandina berries, for example, kill cedar wax wings. Autumn olive (Elaeagnus umbellata), European buckthorn (Rhamnus cathartica), and honeysuckle (Lonicera spp.) fruits provide less energy for birds than native spicebush (Lindera benzoin), gray dogwood (Cornus racemosa), and Virginia creeper-Parthenocissus quinquefolia (4).
Virginia creeper (Parthenocissus quinquefolia) fruits are important winter food source for birds.
Spicebush (Lindera benzoin) leaves are food for spicebush swallow tails and fruits are eaten by birds. Photo by Tom Potterfield on Flickr
About 20% of our native bees are specialists and require specific plant species for survival. For example, the trout lily bee (Andrena erythronii) exclusively feeds on trout lilies (Erythronium spp.). But, trout lilies and other spring species native to the US are being out-competed by species such as fig buttercup (Rununculus ficaria), a native of Eurasia. Often aggressive non-natives like fig buttercup, emerge earlier than our native plants, rob them of the sunlight and out-compete them for resources. Even bees that are generalists and forage on non-native species prefer natives (5).
Trout-lily bees would go extinct if trout-lily plants such as this yellow trout lily (Erythronium americanum) disappear and vice versa. Photo by Janet on Flickr
Fig buttercup (Rununculus ficaria) suffocates our native spring plants. Photo by Ferit GURE on Flickr
Role of gardens in native plant conservation
An estimated 63, 000 square miles of land, about the size of Texas, in the conterminous US has been converted to lawns (6). This means our lawns, backyards and gardens have increased importance in native plant conservation. Ecologists have long told us that there is a strong relationship between the size of an area and the number of species found there. The larger the area, the more diverse the habitat, numerous the species and the more likely a large population of any given species can be supported. If we transform our yards into gardens rich in native plant species, it would provide an interconnected habitat for local and migratory wildlife. In addition, native plants add a sense of place, often lacking in our homogenized landscape.
With 17,000 vascular plants, the US has one of the most diverse flora in the world and one could certainly create a well-designed and beautiful garden entirely out of native plants. However, one need not go that far. A garden with at least 50% native plants, would still make a tremendous difference in native plants and wildlife conservation.
My garden consists of about 80% native plant species but non-natives like sweet william, lily and a peach tree are also present.
Together we can make difference
If you are interested in incorporating native plants into your garden, do not dig them from the wild. Digging wild plants can only be justifiable if it is in danger of being lost permanently due to development and needs rescuing. Many plant nurseries now carry native plants and their inventories of these plants are increasing with demand. Also, keep a look out for native plant sale events near you (see example—spring 2017 native plant sale in Virginia)
Beyond growing natives in our garden, we can actively promote and advocate for them by volunteering with native plant societies. We can support our parks and wild lands which are in many cases the only remaining refuge for native plants and wildlife. Local and national organizations that work towards preserving wild lands need our support. Equally important, we must ask our cities and states to choose native plants over non-natives and often invasive species in parks, community gardens and public spaces including medians, road sides and around hard infrastructure. A paradigm shift is imperative. It is time to consider the ecological impact of our designed landscapes. Let’s create a biodiversity reserve in our gardens and man-made landscapes. Let’s go native!
References
1. Catling, P.M. 2005. Effects of invasive alien plants on birds: some examples from North America. Biodiversity, 6(3):30-39.
2. Flanders, A., Kuvelsky, W., Ruthven, D. III, Zaiglin, R., Bingham, R., Fulbright, T., Hernandez, F. & Brennan, L. 2006. Effects of invasive exotic grasses on South Texas rangeland breeding birds. The Auk, 123(1): 171-182.
3. Steidl, R.J., Litt, A.R. & Matter, W.J. 2013. Effects of plant invasions on wildlife in dessert grasslands. Wildlife Society Bulletin, 37(3):57-536.
4. Smith, S.B., K.H. McPherson, J.M. Backer, B.J. Pierce, D.W. Podlesak, and S.R. McWilliams. 2007. Fruit quality and consumption by songbirds during autumn migration. The Wilson Journal of Ornithology, 119:419–428.
5. Morandin, L.A. & Kremen, C. 2012. Bee preference for native versus exotic plants in restored agricultural. Restoration Ecology, 21(1): 26-32.
6. Milesia, C., Elvidgeb, C.D., Dietzc, J.B., Tuttled, B.T., Nemania, R. R. & Runninge, S.W. 2005. A strategy for mapping and modelling the ecological effects of US lawns in Moeller, M. & Wentz, E. (eds.) Joint Symposia URBAN-URS 2005, 2005 Tempe, AZ, USA. International Society for Photogrammetry and Remote Sensing.