I once was quite proud of the English Ivy tree I’d nurtured in my townhouse garden. I was ignorant of its impact on the environment.
My mother and I had planted a pair of four-inch plants some 20 years before I started shaping them into a tree. I didn’t know that English Ivy was invasive. I knew very little about invasive plants.
That changed when I became a Green Spring Extension Master Gardener in 2014. I learned that invasive plants are a species accidentally or intentionally introduced by humans into a region where those plants did not originate. They can cause great damage to the new area’s natural resources. An invasive species can be any kind of living organism – plant, insect, fish, fungus, bacteria and even seeds or eggs. Species that grow and reproduce quickly and that spread aggressively can be labeled ‘invasive’.
The Virginia Department of Conservation and Recreation (DCR) has created an Invasiveness ranking that categorizes the level of threats to forests and other natural communities and native species from invasive plants. The categories are high, medium and low. Kevin Hefferman, a stewardship biologist at DCR, says the ranking increases for species that:
• Alter natural processes, such as water flow or soil chemistry
• Invade undisturbed natural areas
• Cause substantial impacts on rare or vulnerable native species or natural areas
• Are widely distributed and generally abundant where present
• Disperse readily to new places
• Require significant resources to manage and control
Naturalists encourage gardeners to curb the spread of invasive species by planting native plants and removing invasive ones. There are many web sites that offer native alternatives, including those of the Virginia Native Plant Society, The Master Gardeners of Northern Virginia, and Green Spring Gardens. More information also is available from Master Gardeners at Green Spring.
In full disclosure, I adore English Ivy (Hedera helix). However, I won’t plant it. It’s an evergreen, perennial vine. It grows as a dense ground cover (juvenile stage) and a climbing vine (adult stage). Regretfully, its dense foliage blocks sunlight and restricts growth of other plants. As pretty as it looks growing up mature trees, its heavy vines loosen bark and hold moisture against the trunk, often causing fungal disease and death. Heavy vines also can fell trees in bad weather. English Ivy also nurtures bacterial leaf spot, a disease seen in elms, oaks and maples. It spreads by seeds and runners. Mature vines produce flowers and seeds that birds enjoy and spread. It is also known to cause wildfires to spread as flames climb vine-covered trees. It tends to climb anything it can use for support such as fences, homes or trees.
Invasive species overtake native species and destroy ecosystems that rely upon diversity of species to survive. They often provide little or no food value for wildlife. Kudzu is another devastating invasive plant that grows at a rate of one foot per day with mature vines as long as 100 feet. It engulfs everything in its path from trees to shrubs to homes and cars.
When visiting a plant nursery or accepting plants from friends and neighbors, avoid invasive species. Plant natives for their beauty and for the well-being of the environment.
Author Gioia Caiola Forman is a Green Spring Extension Master Gardener and a board member of the Friends of Green Spring.