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Although some non-native plant species display colorful flowers and are popular as garden ornamentals, they can be highly invasive and destructive to a natural environment. Many introduced, or "exotic" plants were planted to decorate homes and gardens. Over the years, they have escaped cultivation and have infested natural areas. Because they are growing in an environment that lacks natural controls (diseases, predation), they have an advantage over native species and can easily out compete them for habitat. This causes an imbalance in the ecosystem and threatens the biodiversity of the area.

The Kentucky Exotic Pest Plant Council, Kentucky affiliate of the Southeast Exotic Pest Plant Council, has the responsibility of keeping a list of the most severely invasive plant threats to Kentucky. Their current list can be seen at

Kentucky's top 10 worst plant threats:

Bush Honeysuckle rapidly invade and overtake a site, altering habitats by decreasing light availability, depleting soil moisture and nutrients, and possibly by releasing toxic chemicals that prevent other plant species from growing in the vicinity. 

Chinese Silvergrass forms extensive infestations by escaping from older ornamental plantings to roadsides, forest margins, and adjacent disturbed sites, especially after burning.

Garlic Mustard invades a forest through a disturbance such as tree fall or trail construction. Prolific seed production and lack of natural predators allow it to quickly dominate the ground cover. 

Japanese Knotweed spreads quickly to form dense thickets that exclude native species and are of little value to wildlife, leading to it being described as an environmental weed.

Japanese Stiltgrass, also known as Nepalese browntop is especially well adapted to low light conditions. It threatens native plants and natural habitats in open to shady, and moist to dry locations. 

Kudzu smothers, it does not strangle competition, but simply blankets trees with a dense canopy, through which little light can penetrate.

Multi-Flora Rose has invaded a large number of habitats, from hillside pastures, fence rows, rights of way, and roadsides to forest edges and the margins of swamps and marshes.

Oriental Bittersweet is a serious threat to plant communities due to its high reproductive rate, long range dispersal, ability to root sucker and rapid growth rate.

Purple Loosestrife alters the biogeochemical and hydrological processes in wetlands.

Winged Burningbush seeds are eaten and dispersed by birds and other animals, and this has contributed to its spread. Now widely naturalized and invading natural habitats, Winged Burningbush is considered a noxious weed.

What Can You Do To Help?

Each year, Bernheim Arboretum and Research Forest, the Southeast Exotic Pest Plant Council and the Environmental Resource Management Center at Northern Kentucky University publishes a poster of those plants that have proven to be invasive of our native habitats. These introduced plants are out-competing native species resulting in a reduction of plant diversity. We urge everyone to be on the lookout for these plants and avoid planting them in your yard. Instead, there are several similar plants that can provide similar enhancement to your environment. Please view the current and past year's "Kentucky's Least Wanted Plant" posters at

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