Kudzu (Japanese arrowroot) is a grouping of plants from the pea family. As perennial vines that are native to some of the Pacific Islands as well as much of Southeast and eastern Asia, they climb, coil, and trail over anything in their way. Anywhere that kudzu plants become naturalized, they tend to become quite invasive and are, in fact, considered to be a noxious weed. Kudzu climbs and trails over shrubs and trees, growing so rapidly that it will kill them due to the heavy shading they produce.
Kudzu plants were first introduced from Japan to the U.S. in 1876 at the Centennial Exposition in Philadelphia at the Japanese pavilion. In the 1930s and 40s, the vine underwent a rebranding as a method for farmers to halt soil erosion. At that time, field workers earned $8 for each acre where they sowed topsoil with the highly invasive kudzu vines. That cultivation covered more than a million acres with kudzu. These days, it is quite common along roadsides all over the southeastern U.S. going as far north as Pulaski County, IL, mainly in the very rural areas. Kudzu has been described as being capable of spreading at the rate of 150,000 acres (610 km2) per year, however, the United States Forest Service actually estimates the rate at only 2,500 acres annually as of 2015.
Kudzu can spread via vegetative reproduction as well as by rhizomes. Kudzu is also capable of rapidly spreading via the seeds that are contained in its pods, maturing in the fall. Each pod-cluster will produce one to two viable hard-coated seeds, but they can actually end up remaining viable for several years. Then, they can only successfully germinate in persistently soggy soil for five to seven days and at temperatures above 20°C (68°F). After the seeds germinate, the little saplings require a well-drained soil that is capable of retaining high moisture. The kudzu then needs to be receiving as much sun as possible during this stage in their growth and can be quite sensitive to any mechanical disturbances. They can also be easily damaged by high water tables, chemical fertilizers, or long shady periods.
During World War II, the U.S. Armed Forces introduced kudzu to Fiji and Vanuatu for camouflaging their military equipment, and it has since become a major weed there. Kudzu vines have been discovered in other countries as well, including Canada in 2009. It has become a problem in northeastern Australia, has been seen in Switzerland, and in some isolated locations in Northern Italy. And, in 2002, New Zealand declared kudzu to be an “unwanted organism.” It was then added to the Biosecurity New Zealand register. And, here in the U.S., after its introduction from Asia during the late 19th century and then being widely planted in the late 1930s, kudzu has now become the most infamous weed in America.
Controlling kudzu long-term involves simply removing or killing the root crown as well as all rooting runners. The older a crown is, the deeper in the ground it goes. If a portion of the root crown is still remaining following an attempted removal, the plant could grow back. It’s important to note that cutting off any above-ground vines isn’t sufficient for killing the kudzu. Several southern U.S. cities hav undertaking a trial program since 2010 where llamas and goats were used for grazing on kudzu in an effort to bring about a reduction in the widespread growth of this weed. Those cities include Chattanooga, TN, Tallahassee, FL, and Winston-Salem, NC.
Proper lawn care around the edges of lawns is usually required to keep kudzu off of grass. Once established it will kill almost any lawn quickly. Physical removal of kudzu is recommended along with proper weed control practictices.
On a more positive note, kudzu is useful for its fiber (aka ko-hemp) for making paper and clothing, as well as for making compost, lotions, and soap. Other uses include animal feed, basketry, and fiber art, as well as traditional Chinese medicinal uses for its many isoflavones. Kudzu has also been utilized for treating alcoholism for more than a thousand years.