ASK THE MASTER GARDENERS
I’m hearing a lot about invasive plants. What are they and why are they so bad?
Invasive species are non-native plants, animals, fungi or microorganisms that spread rapidly and cause harm to the environment, the economy or human health. Invasives come from all around the world and as international trade increases, so does the potential for introductions of invasive species.
Not all non-native plants (also referred to as “exotic,” “alien,” and “introduced”) are invasive and for the most part they are not harmful. But a species classified as invasive can wreak havoc on our ecosystems.
Invasive plant species are determined by their growth habit. They often have a combination of the following characteristics: fast growth and quick maturity, multiple means of reproduction (many seeds and rhizomes), long growing seasons, monopolization of water and nutrients, blockage of sunlight on land and water, changes in soil composition and hydrology (movement, distribution and quality of water). These effects cost the United States hundreds of millions of dollars each year to control.
Invasive species have few if any natural predators or pathogens in their new environments. Given all these factors falling in their favor, invasive plants have the ability to take over and become a monoculture; this often leads to a drastic decrease in biodiversity in affected areas.
Every year in New York state, invasive plants overrun millions of acres of rangeland, clog waterways and choke agricultural lands. They also out-compete and eliminate native plants upon which insects and animals are dependent.
A prime example is purple loosestrife (Lythrum salicaria), which was brought to North America in the 1800s from Europe. Plants were brought by settlers for their flower gardens. And now purple loosestrife has taken over wetlands, out-competing native species and displacing animals that depend on native plants for food, nesting and shelter.
An even more damaging native plant is kudzu (Pueraria lobata). It was introduced into the U.S. in the late 1800s as an ornamental and was used for erosion control between the 1930s and ’50s. It will cover anything it its path, growing at a rate of 1 foot per day, 60 feet a season with a root system up to 400 pounds. It’s known as “the vine that ate the South” and it’s working its way north.
Another troublesome species, garlic mustard (Alliaria petiolata) was brought over either as an edible herb or accidentally as seeds on boots or in the soil of plants to be transplanted in new settlements. The plants have now taken over forests and are an ongoing invader in some of our gardens.
In order to help reduce the devastating environmental and economic impacts of invasive species, the state Department of Environmental Conservation has proposed regulations to establish requirements for the sale, importation, purchase, transportation or introduction of invasive species and strict guidelines for the sale, cultivation and usage of invasives.
Invasive plants might satisfy our aesthetic needs or provide a solution to a horticultural problem, but their hazard to the ecosystem can’t be overlooked. As conscientious gardeners and homeowners, we can increase the use of native plants and non-invasive species in our yards and gardens, set aside natural areas to preserve native genotypes, remove invasives, encourage nurseries not to carry them and support community efforts to control or eradicate invasive plant monocultures.
Contact your county Cornell Extension for additional information on invasives, their removal and a list other plants that can be substituted.
Mootsy Elliot, master gardener with Cornell Cooperative Extension of Rockland
THE WORST OFFENDERS
Here are a few highly aggressive invasives as defined by the state Department of Environmental Conservation.
European common reed grass (Phragmites australis)
Garlic mustard (Alliaria petiolata)
Black swallow-wort (Cynanchum nigrum)
Japanese stilt grass (Microstegium vimineum)
Oriental bittersweet (Celastrus orbiculatus)
Mile-a-minute vine (Persicaria perfoliata)
Kudzu (Pueraria lobata)
Japanese angelica tree (Aralia elata)
Winged euonymus (Euonymus alatus)