What are invasive plants? How do you keep invasive plants from spreading? Let's dig in!
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Have you ever stopped along a country roadside and dug up a flowering plant near the edge of a drainage ditch, thinking it would make a lovely addition to your garden? Or made a fall wreath from a climbing vine with gorgeous orange berries, then later tossed the wreath into the bushes out behind the garage?
Or maybe youâve decided to let a piece of the lawn go wild to reduce mowing, or bought a piece of land that once pastured farm animals, but has gone âback to natureâ because you keep no livestock.
Thatâs how I got purple loosestrife, a plague of Asian bittersweet, and acres of a thorny shrub called autumn olive. My âbackyardâ also sports impermeable hedges of Japanese knotweed (aka âbambooâ) plus multiflora roses and Japanese barberry. All of these plants are listed and regulated as âinvasive speciesâ in my home state of New Hampshire.
Once established, these non-native plants become challenging or even impossible to remove before they completely dominate a landscape.
What is an âinvasiveâ* plant?
So-called âinvasiveâ plant species generally refer to non-native (aka âalienâ) plants that spread rapidly and threaten economic harm or the health of native ecosystems. Most states have enacted laws and regulations forbidding the sale, importation, or propagation of such species.
According to the Nature Conservancy, invasive species cost the U.S. economy $120 billion a year, with over 100 million acres (an area roughly the size of California) suffering from invasive plant infestations.
All plants have some geographical point of origin, an ecosystem where they co-evolved with numerous other plants, animals, and microorganisms over millennia, to the point where they keep one anotherâs populations in check.
To thrive, plants have evolved many ingenious ways to distribute themselves, among them
- Root systems that spread rapidly and invisibly underground.
- Seedpods that explode when ripe, spitting their seeds far and wide.
- Seeds so light they can float long distances on the wind.
- Seeds carried in the digestive systems of animals that eat their fruits and deposit the seeds some distance away in a little packet of scat that helps fertilize the ground they fall on.
- Seeds with barbs or burrs that stick to the fur of passing animals that transport them to new ground.
Humans took favorite plants with them as they traveled to explore, settle, and exploit new lands, a practice very much with us today. More recently, people have imported non-native species to introduce as ornamental specimens to gardens, to control erosion on disturbed construction sites, or for other purposes. Still other invasives hitched rides on ships transporting agricultural, forestry or other products.
In their new habitats, some (not all) non-native plants spread rapidly, since their new surroundings lack the plant diseases, predators, and strong competition from other plants that kept them under control in their native ecosystems.
Invasives include vines, grasses, herbaceous flowering plants, shrubs, and trees. Invasive vines may strangle native trees and shrubs; grasses, herbaceous species, and shrubs may crowd out native plants. They may reduce biodiversity by strangling or crowding out native species, degrade and destroy habitat, and destroy food webs by providing wildlife with less nutritious seeds or fruits than native plants.
Aquatic/wetland invasives are often spread between and among waterbodies by boats, trailers, and other recreational equipment. These plants may crowd out organisms within the ecosystem, clog waterways, kill or alter the balance of aquatic life.
How to stop the spread of invasive plants
If youâre a landowner, a gardener or farmer, a pond owner, a recreational boating enthusiast, or simply a citizen concerned about the health of your local environment, there are things you can do to help stop the spread of invasive plant species:
- Learn to recognize by sight the invasive species in your area and point them out to others.
- Donât dig anything from the wild unless youâre certain itâs not invasive (or endangered).
- If you do see an invasive on you own property, dig it up, smother it, or follow instructions from your state's invasive species program. Severe infestations may require herbicides.
- Plant native shrubs and flowers. They not only provide best food and shelter for native wildlife and protect the environment from spread of harmful weeds, but they are also easier to maintain.
Learn more about invasive plants
National Invasive Species Information Center (NISIC): Gateway to invasive species information; covering Federal, State, local, and international sources. To find information about invasive species in your state, type the name of your state into the Search NISIC box at the top left of the page.
*Whatâs in a name? Fascinating paper on how why scientists are searching for a new, more neutral framework for describing invasive plants.
The Impacts of Invasive Species
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