Invasive plant species are plants growing outside of their native habitat range. They are most often introduced when they are planted in gardens or yards. Some of these plants are able to reproduce and spread rapidly causing potential harm to our ecosystem. These invasive plants can be harmful because they can out compete and overshadow our native species. There are many invasive plant species in Tennessee and below are a few of the most common.
Image by Richard Webb, Self-employed horticulturist, Bugwood.org
Common Privet (also known as European Privet) is an invasive species found in Tennessee and is listed as a serious threat. Privet is a common invasive species that can be found around old unkempt houses, roadsides, forest, and riverbanks. This species is able to grow in heavy shade cover or with copious light. Privet can reach 16 feet in height and flowers in June. The white flowers grow in clusters and are fragrant. Privet also produces a fruit that is blackish, blue that contains 1 to 4 seeds. These berries are commonly consumed by birds which is how privet has been able to spread so rapidly. The best method to control further spread of plants is to remove plants before seed can be dispersed in the fall.
Image by Theodore Webster, USDA Agricultural Research Service, Bugwood.org
Japanese honeysuckle is a semi-evergreen that has a woody vine that can grow to enormous lengths. The branches can form arbors in tree canopies or in other shrubs. Like kudzu, it can overshadow native species from sunlight which can stunt growth or even kill native species. Japanese honeysuckle leafs out very early in the spring giving it a competitive advantage over many other species and allowing it to grow much more rapidly. From April to August flowers bloom in pairs at the base of the leaf stem. The blossoms are white and contain five stamen and one pistil. The berry is produced between June and late fall. It starts green and ripens to black. Two or three seeds are found on average in each berry. The best method of control is to remove plants in late summer or early fall before the berries and seeds are dispersed. Coral or trumpet honeysuckle are similar native alternatives to use when landscaping.
Image by James H. Miller, USDA Forest Service, Bugwood.org
Kudzu was first introduced to the United States in 1876 at the Philadelphia Centennial Exposition. This climbing vine is native to eastern Asia. Kudzu was introduced as a decorative vine that could help prevent soil erosion. This plant unfortunately thrived in the hot, humid portions of the country and is rapidly spreading in the Southeastern United States. Annually, this semi woody, perennial vine infests an estimated 30,000 square kilometers per year. This plant costs the United States economy millions of dollars a year due to lost crop and forest production. Kudzu grows quickly and can overshadow tall native trees in a matter of years. The root system of Kudzu can reach up to six feet in depth and can take much needed water away from native species. The best way to control and eliminate kudzu is to catch the problem early. Vines can be cut back but the plant will make a quick comeback if the large roots are not removed. Livestock will feed on this vine and can control future growth. Herbicides can be very beneficial in areas of large infestation. Kudzu SHOULD NOT BE PLANTED as it expands uncontrollably. Cross vine is a great native alternative to kudzu.
Image by Barry Rice, sarracenia.com, Bugwood.org
Japanese stiltgrass (also known as Asian stiltgrass) is a common invasive grass in Tennessee that was introduced in 1919. This grass can live in a wide range of areas including lawns, forest edges, ditches, and stream banks. Thriving with or without much light, this grass prefers moist soil conditions and disturbed land. This plant is commonly found in overgrown gardens and along eroded river banks. It can become very dense and prevents native species that would normally grow in the area. This grass can grow up to three and a half feet tall with asymmetrical leaves that can be as long as three inches. One or two flowers spike from the top of each plant. These plants can be self-fertile or can require pollination. Each plant can produce between 100 to 1000 seeds. The seeds can remain in the soil for three years and are spread to new areas with the help of water or soil disturbance. The best method of control is to detect this grass before the population gets too large. Hand pulling can be an effective control because the roots of this plant are very shallow. Once an infestation has been reduced planting Sugarcane Plumbgrass or Indian grass to the area can deter Japanese stiltgrass from sprouting as much the next year.
Information on other invasive plants and control recommendations can be found here: