By Fern Campbell
Piedmont Master Gardener
During Native Plant Month in April, folks in Virginia and across the nation celebrated by planting native trees, shrubs, perennials, vines and grasses to establish habitats that allow our birds, pollinators, and wildlife to thrive. Incorporating native plants into our basic garden designs is imperative to reverse declining populations of our birds and insects and to restore balance to our ecosystems.
Native plants are indigenous to our region and have evolved here over centuries with our local insects, birds and other animals. Together, they make the Virginia Piedmont unique, providing wildlife with food, cover, and places to raise their young—thus supporting biodiversity and forming the basis of the food web and healthy ecosystems.
The stakes are high. According to research published in 2019 by the journal Science, the total breeding bird population in the U.S. and Canada has dropped nearly 30 percent since 1970. Flying insects like moths have declined more than 75 percent since the 1990s. Insects pollinate 90 percent of our flowering plants, and without these insects and other pollinators, we will lose these plants and the food web will collapse.
Because native plants are fully adapted to our local climate and soils, they can thrive in situations where exotic garden plants struggle. Once native plants are established, there should be less need for extra water, chemical applications of fertilizers, or any pesticides, thus protecting our waterways by reducing pollutants and nutrient runoff. Every ecoregion has different native plant communities. We are in the Northern Piedmont Native Plant ecoregion.
It turns out that not just any native plant will do. Plant choice matters.
Studies have shown that the particular native plant selections gardeners make can have a tremendous impact on the diversity of wildlife in our landscapes. Years of observations and research by University of Delaware entomologist Douglas Tallamy and his assistants have revealed that certain species of native plants, which he terms “keystone plants,” play a major role in supporting a healthy food web, particularly for insects and animals that feed on insects. They are also necessary for many wildlife species to complete their life cycle.
In a stone arch, the keystone holds the other stones in place. Take it away, and the arch collapses. In his book The Nature of Oaks, Tallamy describes how keystone plants provide similarly critical support for our local ecosystems. “A yard without keystone plants,” he writes, “will fall far short of the insect abundance necessary to sustain viable food webs, even if dozens of native plant genera are present.”
There are two types of keystone plants, according to the National Wildlife Federation:
1. Host plants that feed the young caterpillars of approximately 90 percent of butterflies, moths and skippers (Lepidoptera). Their foliage serves as nourishment for the protein-rich caterpillars, which in turn are important components in the diets of many animals, including the young of most birds.
2. Plants that feed specialist bees that eat pollen only from certain species. Keystone plants for native bees feed both specialist and generalist bees.
Tallamy’s research finds that 90 percent of what caterpillars eat is created by only 14 percent of native plant species, with only five percent of the powerhouse plants taking credit for 75 percent of food. “Take a keystone native plant like an oak tree. More than 500 caterpillars can eat that oak tree,” Tallamy explains. “That allows for a more complex and more stable food web. These keystone or ‘powerhouse’ plants that support the caterpillars are doing the majority of the work, and without them the food web is doomed.”
In the mid-Atlantic region, we have more than 2,000 native plant genera, of which Tallamy’s team has categorized 38 as keystone plants. Native oaks (Quercus), wild cherries (Prunus), willows (Salix) and birches (Betula) top his list of tree genera. The most powerful herbaceous plants include goldenrods (Solidago), asters (Symphyotrichum), wild strawberry (Fragaria) and perennial sunflowers (Helianthus).
Tallamy makes a compelling case for homeowners to include keystone plant species native to our region in our landscapes. By supporting local insect populations, these plants create more productive landscapes that help restore ecosystems and support the food web. You should select a diversity of native keystone plants to have the most impact, and pick plants suited to your existing soil, moisture, sunlight and other site conditions.
You can learn more about native plants in our area by looking under the Gardening Resources tab on the Piedmont Master Gardeners’ website, piedmontmastergardeners.org. Among other things, you will find a recently updated list of native plants and acceptable cultivars for the Northern Piedmont region, as well as a list of local nurseries and garden centers that carry native plants—the Plant Northern Piedmont Natives Retail Partners. While there, you can download such resources as “Every Garden Needs Keystone Plants,” highlighting keystone plants native to our region, and a series of site-specific plant lists PMG has developed, with titles such as “Cool Plants for Hot Places,” “Cool Plants for Dry Shade,” “A Carpet for Your Garden” (groundcovers) and “Native Plants for Birds.”
Other helpful online resources include the National Wildlife Federation’s plant finder (www.nwf.org/nativeplantfinder/), which offers a guide to native plants by Zip Code. And to hear from Prof. Tallamy himself, search for his You Tube presentation “Native Keystone Plants for Wildlife.”
Again, plant choice matters. Rather than select a plant that is just pleasing to the human eye, choose plants that also support the complex web of life. Healthy ecosystems provide the basic services upon which we all depend. By bringing keystone plants into our yards, we can do our part to support healthy ecosystems and the benefits they provide to humans and wildlife alike.
Keystone Plants Native to Piedmont Virginia
Trees that support up to 500 caterpillar species
- Oaks
- white oak (Quercus alba)
- willow oak (Quercus phellos)
- scarlet oak (Quercus coccinea)
- Birches
- sweet birch (Betula lenta)
- river birch (Betula nigra)
- Pines
- pitch pine (Pinus rigida)
- Virginia pine (Pinus virginiana)
- shortleaf pine (Pinus echinata)
- Maples
- red maple (Acer rubrum)
- boxelder (Acer negundo)
- Cherries
- black cherry (Prunus serotina)
- American plum (Prunus americana)
- Willows
- black willow (Salix nigra)
- upland willow (Salix humilis)
- Dogwoods
- flowering dogwood (Cornus florida)
- pagoda dogwood (Cornus alternifolia)
- silky dogwood (Cornus amomum)
- Hickories
- pignut (Carya glabra)
- shagbark (Carya ovata)
- mockernut (Carya tomentosa)
- Beech
- American beech (Fagus grandifolia)
- Serviceberries
- shadbush (Amelanchier canadensis)
- downy serviceberry (Amelanchier arborea)
Shrubs that support up to 290 caterpillar species
- Blueberries
- highbush (Vaccinium corymbosum)
- lowbush (Vaccinium angustifolium)
- Chokeberries
- red chokeberry (Aronia arbutifolia)
- black chokeberry (Aronia melanocarpa)
- Viburnums
- arrowwood viburnum (Viburnum dentatum)
- blackhaw viburnum (Viburnum prunifolium)
- mapleleaf viburnum (Viburnum acerifolium)
- possumhaw viburnum (Viburnum nudum)
Flowers that support up to 115 caterpillar species
- Asters
- aromatic aster (Symphyotrichum oblongifolius)
- New England aster (Symphyotrichum novae-angliae)
- heart-leaved aster (Symphyotrichum cordifolium)
- white wood aster (Eurybia divaricata)
- Goldenrods
- gray goldenrod (Solidago nemoralis)
- rough-stemmed goldenrod (Solidago rugosa)
- blue-stemmed goldenrod (Solidago caesia)
- showy goldenrod (Solidago speciosa)
- Sunflowers
- woodland sunflower (Helianthus divaricatus)
- narrow-leaved sunflower (Helianthus angustifolius)
- thin-leaved sunflower (Helianthus decapetalus)
