Tropical kudzu

Pueraria phaseoloides is a plant species within the pea family (Fabaceae) and its subfamily Faboideae. It is a promising forage crop and cover crop used in the tropics. It is known as puero in Australia and tropical kudzu in most tropical regions. It is closely related to other species in the genus Pueraria and it is crossable with the other species of Pueraria. The name kudzu does not only refer to P. phaseoloides. It is also used for its close relatives Pueraria montana and P. edulis. P. phaseoloides has different scientific synonyms. Depending on the authors, it is possible that two different variation are citied: P. phaseoloides var. phaseoloides and the bigger and larger P. phaseoloides var. javanica. Pueraria phaseoloides is indigenous from east or from southeast Asia. Today it has been introduced and naturalized in a broad range of other wet tropical environments: Africa, Americas and Australia. Preferentially P. phaseoloides is growing in ruderal situations, such as plantations of cocoa or banana, at low altitudes (often under 600 metres above sea level) in wet evergreen or monsoon forests. P. phaseoloides is capable to growth in a large soil spectrum. Acid soils are not a problem and the pH tolerance is between 4.3 and 8. Pueraria phaseoloides is a deep rooting perennial herb, building a subtuberus. This device allows to resist waterlogged soils and short periods of drought. The aboveground structure can grow up to 30 cm at day and often the steams can reach 20 m of elongation. P. phaseoloides is a twiner and climbs over other plants or anthropogenic objects. The leaves are large and trifoliate, typical for Leguminosae. The single leaflets can have an oval or triangular shape. Their dimension can vary from 2 x 2 cm to 20 x 15 cm. The growing season goes from early spring to late fall in the subtropics and year round in the tropics. Flowers are typical for the Fabales order. The colour ranges from mauve to purple and the dimensions are small and disposed in scattered pairs on a raceme. Mature pods of P. phaseoloides show a black color and hair coat. They are straight or slightly curved and can be sized from 4 to 11 cm. Each pod contains 10-20 seeds. They have a particular squarish form with rounded corner (3 x 2 mm) and have also a black or brown colour. The reproduction of Pueraria phaseoloides can be vegetative or generative. P. phaseoloides shows an epigeal germination. The growth from seedling is in the first three or four months moderately vigorous. Contrarily to Pueraria montana var. lobata, P. phaseoloides does not have a dormant period. Successful growth was observed with a temperature between 22.1 and 27.4 °C, colder environment drastically reducing the development. After the establishment, the plant starts to climb and build tangled mats of over a half meter. It was found that the production of seeds is improved by the possibility to climb. The relatively reduced shade tolerance of P. phaseoloides can be an explanation of this phenomenon. Developed plants can also perform a vegetative reproduction. When vines are in contact with the soil, a new plant can grow from the nodes. This enlarges and forms new crowns with 3 -4 vines each. The conjunction with the parental plant is kept until the second growing season. Pueraria phaseoloides is a diploid species. Depending from the source, the cytological characteristics show different results. The diploid number is probably 20 or 22. Some authors found also 24 chromosomes, this results is disputable. Pueraria phaseoloides can become an invasive species when growing in tropical and subtropical habitats due to its fast growth, its wide seed distribution and its ability to fully cover other plants. P. phaseoloides is one of the most invasive species in the United States.