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Invasive Plants: All Green Isn’t Good

Garlic mustard is one of the worst invasive exotic plants in the Ohio River region. Photo by Mary Reed.

There are unwelcome, harmful plants that invade and spread throughout natural areas, but their green leaves and beautiful flowers often disguise them as innocent and unassuming.

“All green isn’t necessarily good,” says Diana Olszowy, a branch manager with the Division of Forestry in Kentucky’s Department of Natural Resources. Certain plants can grow out of control, ruining the diversity of plant life and killing food sources for other animals. Getting educated about these plants is the best way to keep them under control.

Invasive vs. exotic. Invasive plants are plants that grow out of control and can take over significant portions of a natural habitat (see photo). Exotic plants are ones that are not native to a particular area. Exotic and invasive are not interchangeable terms, because native plants can also be invasive if they start to spread aggressively and grow out of control.

Invasive exotic plants escape their native habitats when their seeds travel by wind, water, animal or human trade. An exotic plant can become invasive because there is nothing natural - insects, predators or forest fungal diseases - to keep it in check. Some common exotic invasive plants in the Ohio River region include garlic mustard, bush honeysuckle, kudzu and Japanese knotweed.

The damage they do. Invasive exotic plants are the most dangerous when they take over the area where multiple species grow. “When you’re dealing with an invasive plant, what it does is (it) actually crowds out where a native plant would normally grow,” Diana says. “They shed out the existing stuff – a lot of the flowers and the ferns that would normally be growing there.”

Animals can be left without the food that native plants provide, which ripples throughout the food chain. Invasive exotic plants can cause problems when they grow over trails and campsites. They also can cause harm in the form of needles, thorns or rashes when skin contact is made with the plants.

Preventive measures. Not planting invasive exotic plants and being aware of what they look like are integral steps to combat them. When landscaping, either ask the nursery or a county extension agent if the plant could become invasive.

“One of the main problems is some of these invasive plants are pretty. They’re used a lot by the nursery industry and often that’s how they get here,” Diana says. “They’re very popular as ornament trees in the landscape.” When landscaping, choosing native plants is always the safest bet. Dogwoods, Carolina rose and spiked blazing star are some native alternatives to invasive exotic plants. Extension offices also offer information on plants native to your particular area.

The Center for Invasive Species and Ecosystem Health recommends that you buy or use firewood close to campsites, clean shoes and camping equipment before leaving an infested area (and between trips) and remove plant parts and seeds from clothing and equipment to avoid spreading seeds. Inform a ranger if you do spot an invasive exotic plant along a trail. Avoiding areas infested with invasive exotic species means being able to recognize them.

Weeding out the problem. Once you know what to look for, you can weed or cut out invasive plants before they grow out of control. The next step is having someone certified use pesticides to deal with the problem, but introducing chemicals into the outdoors is obviously not a natural or preferred solution.

“Know what you have,” Diana says. “If you can catch it early, you can pretty much nip it in the bud.”