Written by: Alison Kilpatrick
Distribution: Kudzu (Pueraria montana var. lobata) is a perennial vine native to China, Korea, Japan, India and eastward through the Philippines (Lindgren, Castro, Coiner, Nurse, & Darbyshire, 2013). Populations of Kudzu have been noted outside of its native range in Australia, New Zealand, Italy, Switzerland, South Africa, South America, Mexico, the United States, and now Canada (Pasiecznik, 2007). Kudzu was introduced into the United States in Pennsylvania and was widely encouraged to be planted by landowners (Forseth & Innis, 2004). It has since naturalized and spread west to Texas, east to Massachusetts, north to Michigan, and south to Florida (Lindgren et al., 2013). There have also been reports of Kudzu on the west coast in Washington and Oregon (Lindgren et al., 2013). Kudzu now covers approximately 3 million hectares of land in the United States and is estimated to be spreading by 50,000 hectares per year (Forseth & Innis, 2004).
Figure 1: Current global distribution of Kudzu, Pueraria montana (Base map: ESRI 2015; Distribution modified from EDDMaps)
Figure 2: Kudzu range within Canada. Kudzu is currently limited to one small population on the shores of Lake Erie near Leamington, Ontario (Base map: ESRI 2015; Distribution modified from EDDMaps).
Habitat: Kudzu’s ability to establish itself in a wide range of conditions makes it a generalist species. It can be found in a wide variety of habitats including forests, shores, floodplains, fields, and disturbed areas (Lindgren et al., 2013). While it thrives in areas that are open and have well-drained, fertile soils, it can establish itself in nutrient-deficient soils due to its ability to fix nitrogen from the atmosphere (Lindgren et al., 2013). Kudzu does not grow well in soils that are shallow or poorly-drained (Lindgren et al., 2013). It can grow in soils ranging from acidic (pH 4.5) to neutral (pH 7.0), but it does not do well in soils that have a high pH (Lindgren et al., 2013). Kudzu is most productive when it has access to full sunlight (Lindgren et al., 2013). It is sensitive to cold, so it is most successful in locations that have mild winters (mean temperature between 5-15°C) and hot summers (mean temperature over 25°C), but its roots are reportedly capable of surviving temperatures as low as -25°C (Lindgren et al., 2013). For optimal growth, Kudzu requires at least 100 cm of precipitation annually, however the mean annual precipitation in the Leamington area is only 93 cm (Lindgren et al., 2013). This population is currently growing on a clay-rich slope on the shoreline of Lake Erie, where the mean temperature in January is -4.6°C and in July it is 22.3°C (Lindgren et al., 2013).
Potential For Infestation: Kudzu exhibits characteristics of r-strategists. It is a perennial that can grow in unstable conditions, allocates little energy into seed production but produces many seeds multiple times, and its seeds have a low probability of surviving the early stage of life (Lindgren et al., 2013). See Table 1 for the summary of Kudzu characteristics that support its classification as an r-strategist.
Table 1: Summary of the reproductive characteristics of Kudzu compared to those of K and r-selected species (Molles & Cahill, 2014; Forseth & Innis, 2004). Kudzu aligns best with the reproductive characteristics of r-strategists.
|Environment||Stable||Unstable||Capable of establishing in disturbed areas|
|Mortality||Higher probability of surviving to adulthood||Lower probability of surviving to adulthood||Most seeds do not establish as seedlings|
|Size||Large bodied||Small bodied||Relatively small herbaceous vine|
|Fecundity||Few offspring at a time||Many offspring at a time||Produces many seeds at a time|
|Frequency of Reproduction||Multiple times over a prolonged period||Once to multiple times over a short period||Produces seeds every season|
|Energy allocation||Higher energy allocated to producing offspring||Lower energy allocated to producing offspring||Low energy allocated to seed production, high energy allocated to extension growth|
Survivorship: Kudzu follows the Type III survivorship curve typical of plants (see Figure 3). Its seeds usually do not successfully establish (Lindgren et al., 2013). Therefore, this species has a low probability of survival in its early stage of life. Once established, Kudzu continues to grow through vegetative reproduction (Lindgren et al., 2013).
Figure 3: Survivorship curves (Image credit: Husthwaite, n.d.)
Dispersal and Vectors: Kudzu produces seeds annually and its seed pods can disperse up to 25 meters but most stay within 6 meters of their origin (Lindgren et al., 2013). However, despite the production of viable seeds, Kudzu seedlings are rare and usually do not survive to the following year when found in the wild (Lindgren et al., 2013). This suggests that seeds are not effectively dispersed or that there is something preventing seedlings from establishing (Lindgren et al., 2013). Therefore, the principal method of propagation of Kudzu is vegetative reproduction rather than sexual reproduction (Lindgren et al., 2013). It spreads through rapid extension growth and frequent rooting of stems that contact the soil (Forseth & Innis, 2004). Humans are a primary vector for Kudzu dispersal as most long-distance dispersal has been through intentional planting by humans (Forseth & Innis, 2004). Kudzu’s method of introduction into Ontario is currently undetermined, though several possibilities have been considered including water dispersal across Lake Erie, bird dispersal, disposal of farming materials, or intentional planting for stabilization of the shore (Lindgren et al., 2013). However, there is insufficient evidence to support any of these methods as the source for the population in the Leamington area (Lindgren et al., 2013).
Special Considerations: Kudzu is an aggressive competitor because its rapid growth rate allows it to smother and shade other species before they can establish (Forseth & Innis, 2004). In addition, a compound that inhibits seed germination and plant growth has been found in Kudzu root and leaf extracts (Lindgren et al., 2013). High concentrations of this compound found in soil following Kudzu decomposition could be enough to result in allelopathic effects on some plant species (Lindgren et al., 2013). Through its ability to fix nitrogen in the atmosphere, Kudzu can alter an ecosystem’s nitrogen cycles and can potentially affect regional air quality (Forseth & Innis, 2004; Lindgren et al., 2013).
EDDMapS (2017). Kudzu: Pueraria montana var. lobata (Willd.) Maesen & S. Almeida. Early Detection & Distribution Mapping System. The University of Georgia – Center for Invasive Species and Ecosystem Health. Retrieved January 26, 2017 from https://www.eddmaps.org/distribution/viewmap.cfm?sub=2425
Forseth, I. N, Jr. & Innis, A. F. (2004). Kudzu (pueraria montana): History, physiology, and ecology combine to make a major ecosystem threat. Critical Reviews in Plant Sciences. 23(5):401-413.
Husthwaite, R. (n.d.). Survivorship curves [image]. Retrieved January 26, 2017 from https://en.wikipedia.org/wiki/Survivorship_curve
Lindgren, C. J., Castro, K.L., Coiner, H. A., Nurse, R. E., & Darbyshire, S. J. (2013). The biology of invasive alien plants in Canada (12): Pueraria montana var. lobata (Willd.) Sanjappa & Predeep. Canadian Journal of Plant Science. 93:71-95, doi:10.4141/cjps2012-128
Molles, M., & Cahill, J. (2014). Ecology: concepts and applications (3 edition). New York: McGraw-Hill.
Pasiecznik, N. (2007). Pueraria montana var. lobata (kudzu). Invasive Species Compendium. Retrieved January 26, 2017 from http://www.cabi.org/isc/datasheet/45903