Kudzu

Kudzu (クズ or 葛), Pueraria lobata (syn. P. montana, P. thunbergiana), is one of about 20 species in the genus Pueraria in the pea family Fabaceae, subfamily Faboideae. It is native to southern Japan and southeast China in eastern Asia. The name comes from the Japanese word for this plant, kuzu. The other species of Pueraria occur in southeast Asia, further south.

Description
Kudzu is a climbing, woody or semi-woody, perennial vine capable of reaching heights of 20–30 m (66-98 ft) in trees, but also scrambles extensively over lower vegetation. The leaves are deciduous, alternate and compound, with a petiole (leaf stem) 10–20 cm (4–8 in) long and three broad leaflets 14–18 cm (6–7 in) long and 10 cm (4 in) broad. The leaflets may be entire or deeply 2–3 lobed, and are pubescent underneath with hairy margins. The flowers are borne in long panicles 10–25 cm (about 4–10 in) long with about 30–80 individual blooms at nodes on the stems (see image).

Each flower is about 1–1.5 cm (about 0.4–0.6 in) long, purple, and highly fragrant. The flowers are copious nectar producers and are visited by many species of insects, including bees, butterflies and moths. Flowering occurs in late summer and is followed by production of brown, hairy, flattened seed pods in October and November, each of which contains three to ten hard seeds. Seeds, however, are only produced on plants that are draped over vegetation, fences, and other objects. Only one or two viable seeds are produced in a cluster of seed pods.

Once established, these plants grow rapidly, extending as much as 20 m (60 ft) per season at a rate of about 30 cm (12 in) per day. This vigorous vine may extend 10–30 m (30–100 ft) in length, with basal stems 1–10 cm (1–4 inches) in diameter. Kudzu roots are fleshy, with massive tap roots 10–20 cm (4–8 in) or more in diameter, reaching depths of up to 12 feet in older patches, and weighing as much as 180 kg. As many as thirty stems may grow from a single root crown.

Kudzu grows well under a wide range of conditions and in most soil types. Preferred habitats are forest edges, abandoned fields, roadsides, and disturbed areas, where sunlight is abundant. Kudzu grows best where winters do not drop below −15 °C (5 °F), average summer temperatures are regularly above 27 °C (80 °F), and annual rainfall is 1000 mm (40 in) or more. This fast growing plant does not do as well in less temperate areas.

Food
The non-woody parts of the plant are edible. The young leaves can be used for salad or cooked as a leaf vegetable; the flowers battered and fried (like squash flowers); and the starchy tuberous roots can be prepared as any root vegetable. The starchy roots are ground into a fine powder and used for varieties of Wagashi and herbal medicines. When added to water and heated, kudzu powder becomes clear and adds stickiness to the food. It is sometimes known as "Japanese arrowroot", due to the similar culinary effect it produces.

Its leaves are high in vitamins A and C, as well as calcium and protein. Its roots are rich in starch and its flowers are an excellent honey source.

The name Kudzu appeared first in Kojiki and Nihonshoki as a type of vine or Kazura used commonly by the people who lived in Kuzu, an area around present-day Yoshino, Nara prefecture. It is unclear whether the name was taken from the people or the name of the plant was applied to the people. Kudzu has been in use for over 1300 years and it is speculated that it goes back even further. Records from the Nara and Heian era indicate that kudzu was collected and sent as a part of tax. Even today, "Yoshino Kudzu" has the best image of kudzu powder yet. The Kagoshima prefecture is the largest producer of kudzu products.

Jelly
The purple flowers of Kudzu are also used to make a sweet jelly. This jelly is known better in the southern United States. This jelly has been described as tasting like either a cross between apple jelly and peach jelly or bubblegum. The viscous substance has a golden yellow color.

Medicine
Studies have shown that kudzu can reduce both hangovers and alcohol cravings. A person who takes kudzu, will still drink alcohol; however, they will consume less than if they had not taken kudzu. The mechanism for this is not yet established, but it may have to do with both alcohol metabolism and the reward circuits in the brain. The Harvard Medical School is studying kudzu as a possible way to treat alcoholic cravings, by turning an extracted compound from the herb into a medical drug.

Kudzu also contains a number of useful isoflavones, including daidzein (an anti-inflammatory and antimicrobial agent), daidzin (a cancer preventive) and genistein (an antileukemic agent). Kudzu is a unique source of the isoflavone puerarin. Kudzu root compounds can affect neurotransmitters (including serotonin, GABA, and glutamate) and it has shown value in treating migraine and cluster headache.

In traditional Chinese medicine, where it is known as gé gēn (葛根), kudzu is considered one of the 50 fundamental herbs. It is used to treat tinnitus, vertigo, and Wei syndrome (superficial heat close to the surface).

Soil improvement and preservation
Kudzu has been used as a form of erosion control and also to enhance the soil. As a legume, it increases the nitrogen in the soil via a symbiotic relationship with nitrogen-fixing bacteria in the soil. Its deep tap roots also transfer valuable minerals from the subsoil to the topsoil, thereby improving the topsoil. In the deforested section of the Central Amazon Basin in Brazil, it has been used to improve the soil pore-space in clay latosols and thus freeing even more water for plants than in the soil prior to deforestation. .

Animal feed
Kudzu can be used by grazing animals as it is high in quality as a forage and greatly enjoyed by livestock. It can be enjoyed up until frost and even slightly after. Kudzu hay typically has a 15–18% crude protein content and over 60% total digestible nutrient value. The quality of it decreases, however, as vine content increases relative to the leaf content. Kudzu also has low forage yields despite its great deal of growth, yielding around two to four tons of dry matter per acre annually. It is also difficult to bale due to its vining growth and its slowness in shedding water. This makes it necessary to place kudzu hay under sheltered protection after being baled. Kudzu is readily consumed by all types of grazing animals, yet frequent grazing over 3 to 4 years can ruin stands. Thus kudzu only serves well as a grazing crop on a temporary basis.

Other uses
In the Southern United States, where the plant has been introduced with devastating environmental consequences, kudzu is used to make soaps, lotions, jelly, and compost. It has even been suggested that kudzu may become a valuable asset for the production of cellulosic ethanol.

Invasive species
Kudzu was introduced from Japan into the United States in 1876 at the Philadelphia Centennial Exposition, where it was promoted as a forage crop and an ornamental plant. From 1935 to the early 1950s the Soil Conservation Service encouraged farmers in the southeastern United States to plant kudzu to reduce soil erosion as above, and the Civilian Conservation Corps planted it widely for many years.

However, it would soon be discovered that the southeastern US has near-perfect conditions for kudzu to grow out of control — hot, humid summers, frequent rainfall, temperate winters with few hard freezes (kudzu cannot tolerate low freezing temperatures that bring the frost line down through its entire root system, a rare occurrence in this region), and no natural predators. As such, the once-promoted plant was named a pest weed by the United States Department of Agriculture in 1953.

Kudzu is now common throughout most of the southeastern United States, and has been found as far north as Paterson, New Jersey, and as far south as Key West, Florida. It has also been found growing (rather inexplicably) in Clackamas County, Oregon in 2000. Kudzu has naturalized into about 20,000 to 30,000 square kilometers of land in the United States and costs around $500 million annually in lost cropland and control costs.

Kudzu is also becoming a problem in northeastern Australia and has been seen in yet isolated spots in northern Italy (Lago Maggiore).



The spread of kudzu is mainly by vegetative expansion by stolons (runners) that root at the nodes to form new plants and by rhizomes. Kudzu will also spread by seeds, which are contained in pods and mature in the autumn, although this is rarer. One or two viable seeds are produced per cluster of pods. These hard-coated seeds may not germinate for several years, which can result in the re-appearance of the species years after it was thought eradicated at a site.

Control
For successful long-term control of kudzu, it is not necessary to destroy the entire root system, which can be quite large and deep. It is only necessary to use some method to kill or remove the kudzu root crown and all rooting runners. The root crown is a fibrous knob of tissue that sits on top of the root (rhizome). Crowns form from vine nodes that root to the ground, and range from pea-size to basketball-size. The older the crown, the deeper they tend to be found in the ground because they are covered by sediment and plant debris over time. Nodes and crowns are the source of all kudzu vines, and roots cannot produce vines. If any portion of a root crown remains after attempted removal, the kudzu plant grows back.



Mechanical methods of control involve cutting off crowns from roots, usually just below ground level. This immediately kills the plant. Cutting off vines is not sufficient for an immediate kill. It is necessary to destroy all removed crown material: Buried crowns can regenerate into healthy kudzu. Transporting crowns in soil removed from a kudzu infestation is one common way that kudzu "miraculously" spreads and shows up in unexpected locations.

Close mowing every week, regular heavy grazing for many successive years, or repeated cultivation may be effective, if this serves to deplete root reserves. If done in the spring, cutting off vines must be repeated as regrowth appears to exhaust the plant's stored carbohydrate reserves. Cut kudzu can be fed to livestock, burned, or composted.

Late-season cutting should be followed up with immediate application of a systemic herbicide to the cut stems, to encourage transport of the herbicide into the root system. Repeated applications of several soil-active herbicides have been used effectively on large infestations in forestry situations.

Prescribed burning is also used on old extensive infestations in order to remove vegetative cover and promote seed germination for removal or treatment. It is usually done to prepare for treatment of the root crowns. Landscape equipment, such as a skid loader ("Bobcat"), can also remove biomass. While fire is not an effective way to kill kudzu, equipment such as skid loaders can remove crowns and thereby kill kudzu with minimal disturbance of soil.

Efforts are currently being organized by the U.S. Forest Service to search for biological control agents for kudzu. Several fungi are pathogenic to kudzu. Colletotrichum gloeosporioides is one tested example.

The city of Chattanooga, Tennessee has undertaken a trial program using goats and llamas that graze on the plant. The llamas serve double-duty as defense against predators due to their aggressive nature. Currently the goats are grazing along the Missionary Ridge area in the east of the city.