This is National Invasive Species Awareness Week. It’s a time when organizations like the Piedmont Master Gardeners redouble efforts to help our communities recognize the impacts of aggressive, nonnative species on our natural areas, our native flora and fauna, and our overall well-being, and what we can do to address this threat.
Here in the Charlottesville-Albemarle County area, it’s easy to see that we have a serious invasive plant problem. Vast expanses of kudzu stretch across public and private lands in and around the city. Other invasive vines—porcelain-berry, Japanese honeysuckle, English ivy, Asiatic bittersweet—overwhelm our trees or strangle them with their encircling grip. Huge tangles of invasives make large sections of local parkland inaccessible.
Thickets of Japanese knotweed line many of our local stream banks, releasing chemicals that inhibit the growth of other plants and leaving bare earth beneath the dense jungle of stalks and foliage. The annual emergence of Japanese stiltgrass also keeps other plants—even trees—from sprouting under its rapidly spreading mats.
And more and more in our area, we are seeing the damaging effects of tree-of-heaven (Ailanthus altissima), the preferred host of another invasive species, the spotted lanternfly. Honeydew, the sugary secretions from these sap-sucking insects, rains down from the infested trees. This causes sooty mold to form on underlying plant life, which in turn blocks the sunlight these plants need to thrive.
People in our community are working together to combat this problem. The Piedmont Master Gardeners are among the nonprofit organizations and government agencies in the Charlottesville Invasive Plant Partnership, or CHIPP. Its mission is simple: to inspire awareness and action to protect our native species—particularly our tree canopy—from invasive plants. Fulfilling this mission, however, is daunting, given the enormity of the problem.
Other CHIPP partner organizations include Urban Forestry in Charlottesville Parks & Recreation, Charlottesville’s Office of Sustainability, and the Charlottesville Tree Commission, as well as Blue Ridge PRISM (Partnership for Regional Invasive Species Management), Botanical Garden of the Piedmont, Charlottesville Area Tree Stewards, Rivanna Conservation Alliance, Rivanna Master Naturalists, ReLeaf Cville, and Virginia Native Plant Society.
CHIPP is working collaboratively with neighborhoods to survey and quantify the number of trees suffering the impacts of invasive vines and is teaching residents how to identify trees and harmful vines and how to manage invasive vegetation safely and efficiently. At the same time, hundreds of volunteers and professionals in CHIPP’s partner organizations are engaged in raising awareness of the invasive plant crisis, enacting policies to address the problem, and physically removing invasives from our public greenspaces.
To be clear, only a small fraction of introduced, nonnative plant species will become invasive. Many nonnatives adorn our yards and gardens without escaping into the countryside and endangering our natural heritage. Of the nonnative plants brought into this country, either on purpose or by accident, only 10 percent become established—in other words, capable of growing and reproducing without human help. Of these, only 10 percent become invasive.
If the portion of nonnative species that become invasive is so small, why should we care? It’s because these plants have an outsized effect on our environment. Lacking natural predators and often possessing multiple reproductive strategies, invasives quickly overwhelm both native and nonnative plants in our parks, forests, gardens and farms.
For example, invasives decrease biodiversity. To thrive, most wildlife species require some degree of diversity in species composition and forest structure—vegetation with varying heights, widths and shapes. Areas that are highly invaded are composed of very few species, with little variation in shape and height. In short, all the sites look the same and provide limited resources for wildlife.
Invasive plants also outcompete and displace native plants that provide vital food and nesting places for wildlife, particularly native bees, our most important pollinators. Many of our native bees rely exclusively on a single plant or a related group of plants as a food source and are unable to feed on nonnative invaders.
A prime example of an invasive that can crowd out other plants and create ecological dead zones is autumn olive (Elaeagnus umbellata). Listed under Virginia administrative code as a noxious weed, this aggressive plant sweeps in to occupy old fields and the edges of woodlands.
Like many invasive plants, autumn olive (at right) was introduced intentionally, brought to these shores from Asia in the 1830s. Also like many other invasives, autumn olive possesses intrinsic traits that help it outpace the growth of beneficial plants. Symbiotic bacteria associated with autumn olive’s roots make nitrogen available to the plant, allowing it to grow rapidly in soils low in organic matter and nutrients.
Another intrinsic advantage is its ability to produce abundant seed-bearing berries, up to 30 pounds in a single season. The berries are junk food for birds and other animals, which disperse the seeds widely after eating the sugary fruit. Unfortunately, these berries are low in nutrition, lacking the fat birds need for winter migration.
Preventing invasive plants like autumn olive from being sold in the nursery trade is one of the top policy priorities of the agencies and organizations working to keep invasives from running rampant in Virginia. Sadly, dozens of the 103 plants on the Virginia Department of Conservation and Recreation’s official invasives list can still be purchased in nurseries, garden centers or online.
Last year, Virginia passed a law that requires retailers of outdoor plants to post “in a conspicuous manner” signage identifying a plant as invasive and encouraging consumers to ask about alternatives. To take effect in 2027, the law covers 39 specific plants, including English ivy, which blankets countless trees in our community, and Japanese barberry (at left), known to invade wooded areas. Dense stands of the spiny plant have been found to harbor the black-legged tick, a carrier of Lyme disease.
Every advance in this battle makes a difference. It will help restore healthy ecosystems; build communities that are better able to withstand drought, floods and wildfires; and make us more resilient in the face of a changing climate.
Adapted from an article prepared by the Charlottesville Invasive Plant Partnership