Kudzu is an invasive plant species in the United States, introduced from Asia with devastating environmental consequences, earning it the nickname "the vine that ate the South." It has been spreading rapidly in the Southern United States, "easily outpacing the use of herbicide, spraying, and mowing, as well increasing the costs of these controls by $6 million annually." Estimates of the vine's spread vary, from the United States Forest Service's 2015 estimate of per year to the Department of Agriculture's 2009 estimate of as much as annually. Proponents of the newer figure argue that the spread of kudzu has been overblown compared to greater threats such as Asian privet and invasive roses. They argue that kudzu's preference for edge habitats with high sun exposure (such as wooded roadsides) makes it appear more numerous than it actually is to casual observers.
History and biology Description Kudzu is a perennial vine from the bean family Fabaceae and is native to Asia, primarily subtropical and temperate regions of China, Japan, and Korea,Harrington, Timothy B., Laura T. Rader-Dixon, and John W. Taylor. "Kudzu (Pueraria Montana) Community Responses to Herbicides, Burning, and High-density Loblolly Pine." Weed Science,965-974, 2003.Hickman, Jonathan E., Shiliang Wu, Loretta J. Mickey, and Manuel T. Lerdau. "Kudzu (Pueraria Montana) Invasion Doubles Emissions of Nitric Oxide and Increases Ozone Pollution." Proceedings of the National Academy of Sciences of the United States of America, Vol. 107.22, 10115-10119, 2010. with trifoliate leaves composed of three leaflets.Conservation Commission of Missouri. "Kudzu." Missouri Department of Conservation,2011. Five species in the genus Pueraria (P. montana, P. lobata, P. edulis, P. phaseoloides and P. thomsoni) are closely related and kudzu populations in the United States seem to have ancestry from more than one of the species. Each leaflet is large and ovate with two to three lobes each and hair on the underside. The plant has the ability to fix atmospheric nitrogen, which can supply up to 95% of nitrogen needed for its foliage in poor soils. Along the vines are nodes, points at which stems or tendrils can propagate to increase support and attach to structures. As a twining vine, kudzu uses stems or tendrils that can extend from any node on the vine to attach to and climb most surfaces.Black, R.J. and Meerow, A.W. "Landscaping to Conserve Energy" Proceedings of the Florida State Horticultural Society, Vol. 102, 142-144. 1989. In addition, the nodes of the kudzu vine have the ability to root when exposed to soil, further anchoring the vine to the ground. The roots are tuberous and are high in starch and water content, and the twining of the plant allows for less carbon concentration in the construction of woody stems and greater concentration in roots, which aids root growth. The roots can account for up to 40% of total plant biomass.
Kudzu's primary method of reproduction is asexual vegetative spread (cloning) which is aided by the ability to root wherever a stem is exposed to soil. For sexual reproduction, kudzu is entirely dependent on pollinators.
Although kudzu prefers forest regrowth and edge habitats with high sun exposure, the plant can survive in full sun or partial shade. These attributes of kudzu made it attractive as an ornamental plant for shading porches in the southeastern United States, but they facilitated the growth of kudzu as it became a "structural parasite" of the South, enveloping entire structures when untreated and often referred to as "the vine that ate the South."McGroarty, Michael J. "Kudzu, the Vine That Ate the South." How To Control Kudzu, 2010
The word "kudzu" comes from the Japanese word for the plant, 葛, or kuzu.
Origin in Asia Kudzu probably originated in Japan or China, where the ecosystem (primarily the tendency of kudzu to experience above-ground die-back over winter) kept the vine from becoming a nuisance, and it is thought to have been introduced to China and likely Korea.
In Japan, kudzu thrives in mountainous regions, ranging from the 44th parallel north (the island of Hokkaido) to the 30th parallel north (the island of Kuchinoshima) and many of the lowlands and the islands. In Korea, kudzu grows in areas where the temperature can drop to .
History of US introduction The kudzu plant was introduced to the United States from Japan in 1876 at the Centennial Exposition in Philadelphia.Keung, W.M. and Vallee, B.L. "Kudzu Root: An Ancient Chinese Source of Modern Antidipsotrophic Agents." Phytochemistry, Vol. 47, 499-506, 1998. Kudzu was introduced to the Southeast in 1883 at the New Orleans Exposition. The vine was widely marketed in the Southeast as an ornamental plant to be used to shade porches,Frye, Matthew J., Judith Hough-Goldstein, and Jiang-Hua Sun. "Biology and Preliminary Host Range Assessment of Two Potential Kudzu Biological Control Agents." Environmental Entomology, Vol. 36, 1430-1440, 2007. and in the first half of the 20th century, kudzu was distributed as a high-protein content cattle fodder and as a cover plant to prevent soil erosion. It was cultivated by Civilian Conservation Corps workers as a solution for the erosion during the Dust Bowl. The Soil Erosion Service recommended the use of kudzu to help control erosion of slopes which led to the government-aided distribution of 85 million seedlings and government-funded plantings of kudzu which paid . By 1946, it was estimated that of kudzu had been planted. When boll weevil infestations and the failure of cotton crops caused farmers to abandon their farms, kudzu plantings were left unattended. The climate and environment of the Southeastern United States allowed the kudzu to grow virtually unchecked. In 1953 the United States Department of Agriculture removed kudzu from a list of suggested cover plants and listed it as a weed in 1970. By 1997, the vine was placed on the "Federal Noxious Weed List." Kudzu was removed from the list of Federal Noxious Weeds in 2000 with the repeal of sections 2801 through 2813 of the Federal Noxious Weed Act of 1974, which were superseded by updated legislation; however it is still listed as a noxious weed in various states. Today, kudzu is estimated to cover of land in the southeastern United States, mostly in Alabama, Georgia, Tennessee, Florida, North Carolina, South Carolina, Eastern Kentucky and Mississippi. It has been recorded in Nova Scotia, Canada, in Columbus, Ohio, and in all five boroughs of New York City.
Uses and cultivation In the United States, kudzu has been used as livestock feed, in fertilizer, and in erosion control, and the vines have been used for folk art. In Korea, kudzu root is harvested for its starch, which is used in various foods including naengmyon, as well as a health food and herbal medicine. In China, kudzu root is used in herbal remedies, teas, and the treatment of alcohol-related problems. The efficacy of the treatment of alcohol-related problems is currently under question, but experiments show promising results. In Japan, the kudzu root starch (or kuzu root starch) extracted from kudzu roots is used in cooking and natural medicines, and it is used to make hay that sick animals will eat. The starch is used in Japanese cuisine, and is widely consumed as such in that country. Kudzu is also used as a food crop in Java, Sumatra, and Malaya, and can be found in Puerto Rico and South America.
Other uses may include: paper products, food products, insect repellents (the smoke from burning leaves), honey, and methane production.
Kudzu also has potential as a source for biofuel.Marshall, Jessica "Kudzu Gets Kudos as a Potential Biofuel"Kudzu Gets Kudos as a Potential Biofuel, 2008
Ecology in and effect on new communities
New communities Kudzu was intentionally introduced to North America by the Soil Erosion Service and Civilian Conservation Corps in the 1930s for the purpose of controlling soil erosion in the American Southeast. When kudzu was first introduced in the southeast, it was initially used as an ornamental vine to shade homes. By the early 20th century, southerners began to use kudzu for purposes other than ornamentation and so kudzu began to come closer in contact with the land which, in turn, encouraged its spread throughout the southeast. In the 135 years since its introduction, kudzu has spread over three million hectares (ha) of the southern United States, and continues to "consume" the south at an estimated rate of per year, destroying power lines, buildings, and native vegetation, according to a 2006 study. This claim, however, was disputed in 2015 with the United States Forest Service estimating an increase of per year. In the United States, kudzu is extensively reported in Alabama, Arkansas, Washington, D.C., Delaware, Florida, Georgia, Illinois, Indiana, Kentucky, Louisiana, Maryland, Missouri, Mississippi, North Carolina, North Dakota, New Jersey, Oregon, Ohio, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, and West Virginia. Of these states, three in the southeast have the heaviest infestations: Georgia, Alabama, and Mississippi.
Ecological relationships Kudzu kills or damages other plants by smothering them under a blanket of leaves, encompassing tree trunks, breaking branches, or even uprooting entire trees. Kudzu's ability to grow quickly, survive in areas of low nitrogen availability, and acquire resources quickly allows it to out-compete native species. Of the plants that can successfully compete with kudzu, many are other invasive species such as the Chinese privet and the Japanese honeysuckle. In the southeast, the spread of kudzu is especially troublesome because of the high level of biodiversity in this region that is not found in other regions of the United States. Kudzu and other invasive weeds pose a significant threat to the biodiversity in the southeast. They reduce the environment to impoverished "vine barrens." The fast growth and high competitive ability is achieved through several key features of kudzu that are detailed below.
Kudzu is a very stress-tolerant plant. Kudzu is drought tolerant and only the above ground portions of the plant are damaged by frost. Kudzu also forms symbiotic relationships with nitrogen-fixing bacteria to convert atmospheric nitrogen (N2) into ammonium which can be used by surrounding plants. Now the dominant nitrogen-fixing plant in the eastern United States, kudzu fixes an estimated of nitrogen per year, which is an order of magnitude higher than the rates of native species. This ability allows it to flourish in nitrogen-poor sites where other plants are unable to grow. In the absence of other plants, nitrogen then builds up in the soil, allowing the maintenance of large leaf areas and high photosynthetic rates.
While little research has been conducted on the impacts of plant invasion on atmospheric conditions, a study conducted at Stony Brook University in New York shows that kudzu has increased the concentration of atmospheric NOx in the eastern United States, which causes a 2 ppb increase in ground level ozone during high temperature events in addition to soil acidification, aluminum mobilization, and leaching of nitrate (NO3−) into aquatic ecosystems.