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How to identify invasive plants

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It is critical that gardeners learn to identify invasive plants and follow the regimens needed to keep them from taking over the garden
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Invasive plants can be easy to identify, once you know a few things about them.

Ordinarily, gardeners count their success by how well their plants grow. All gardeners expect to enhance that growth by pulling some weeds. One class of weeds, however, can completely overwhelm both garden and gardener. Thus it is critical that gardeners learn to identify invasive plants and follow the regimens needed to keep them from taking over the garden. Fortunately, a variety of organizations and agencies can help both farmers and home gardeners control and eradicate invasive plants.


The History of Invasive Plants

The road to invasive plants is often paved with good intentions. From the 1930s through the 1950s farmers in southern states were encouraged to plant kudzu for erosion control. Southern hospitality is legendary; but little did government agencies advising farmers to plant kudzu know that southern climate and soil conditions were so hospitable that vines would accelerate from energetic to aggressive, covering and smothering crops, shrubbery, trees and farm buildings.

To this day, kudzu is a southern plague. Those who say you can practically see it growing have nicknamed it the mile-a-minute vine. Its massive tap roots and rooted nodes that support new vines make clearing kudzu a truly strenuous task.

Plants in Survival Mode

Japanese knotweed, described by one writer as an escaped ornamental, has aggressive rhizomes that support its rapid spread. The weed can sprout from any fragments left behind in clearing.

Oriental bittersweet, originally regarded as a brighter, more colorful vine than its American cousin, possesses parasitic qualities that enable it to suck sap from the trees it climbs, eventually killing its host. In addition to tenacious root systems, some invasive plants emit toxins which impair or prevent the growth of surrounding plants.


Mugwort is a member of the Artemesia family. Other members of the family, known as wormwoods appear in the Bible and are famous as the toxic ingredient in French absinthe. The Artemesia family has used its self-protective qualities to survive for centuries.

Garlic mustard, recently labeled as invasive in several states, combines an allopathic (toxin-emitting) root system with what is described as a ballistic seed-dispersal system. When pods pop, seeds are shot as many as 10 feet from the mother plant. What a remarkable way to be launched into new life!

How to Handle Invasives

What's a poor gardener to do in the face of invasives? Physical removal and chemical means are the main two choices. Governmental agricultural agencies, organic and other gardening associations, university agricultural extension offices and gardening catalogs all offer guidance and materials for removing invasives.

Regional advice is invaluable. A plant that is invasive in one area of the country may be harmless in another region where the climate and soil do not support aggressive or out-of-control growth. Some plants may be on possible watch lists. This is information about growth habits and problems that will help determine whether a plant is later labeled invasive.

And while many gardeners increasingly regard chemical remedies as the last resort for controlling or eradicating unwanted plants, getting good advice about effective chemical use will prevent harm to wanted plants, birds, beneficial insects and neighboring streams, rivers or ponds.  

Physical Removal


If physical removal is the best deterrent to spreading invasives, regional or local advice can make removal more effective. Knowing how long it takes new plants to appear after a thorough weeding, anticipating the blooming and seed-dispersal cycles of mature plants and knowing how much of a plant must be removed to eradicate growth make physical methods, whether by machine or by hand, yield a greater degree of success than poorly-informed, rage-driven bouts of weeding.

Other Strategies


There are also good strategies to prevent the return of invasive plants. Closer planting of wanted plants make it harder for invasives to settle in again. Decorative plants known for rapid growth and tenacious root- or rhizome-systems like iris or daylilies take up space needed for aggressive invasives to flourish. Nurseries can offer soil enhancements and fertilizers to strengthen the health of wanted plants. You might consider changes to soil chemistry that provide greater hospitality to native plants and less to the invaders.

One of the most exciting aspects of the gardening experience is the opportunity to learn. Every season provides its lessons and triumphs. As you learn to identify invasive plants and prevent their taking over your garden, you will discover that you have learned more than you ever believed possible. The beauty of your garden will continue to spur you on and remind you that invasive plants do not have to win.

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