Contact: Heather Coiner, University of Toronto | h.coiner@utoronto.ca | 416-946-8115
ANNAPOLIS, MD (August 4, 2008) – Once hailed as the “savior of the South”, now reviled as a “scourge”, kudzu (Pueraria montana var. lobata) has consistently excited popular passions. Kudzu’s fast-growing vines climb by twining around structures and vegetation, killing underlying plants by shading them from the sun. In this way it converts ecosystems to vast kudzu monocultures and renders the underlying land useless. Kudzu stems can grow at rates of up to 7 inches per day in the warmest months of the year, which is why it has been chosen as the MISC invader of the month for August.
Kudzu is a semi-woody vine native to southeast Asia. In North America, it is found in sunny disturbed areas along roadsides, railroad and river embankments, forest edges and in old fields. A member of the bean family, kudzu fixes nitrogen in addition to storing a great deal of water and carbohydrates in its roots. During the growing season, kudzu produces a thick canopy of large alternating leaves. Each leaf has three lobed leaflets, and both the leaves and stems are covered in fine hairs. In autumn the leaves fall, leaving behind a tangle of dead and living stems that have a distinctive white central pith.
Kudzu reproduces prolifically and asexually within a patch, when stem nodes take root to establish new independent crowns. Occasionally, kudzu also produces aromative clusters of pink-purple flowers in late summer that later develop into clusters of flat dry hairy pods. Because flowers are infrequent, seed dispersal is widely believed to be unimportant in establishing new populations, although this assumption is currently under investigation. For spread over long distances, it seems more likely that uprooted crowns and severed stems are transported to new areas in soil or by vehicles, roadside mowers, and other machinery.
First introduced in 1876 at the Philadelphia Centennial Exhibition, kudzu was planted to adorn southern porches before being taken up by farmers as an easy-to-grow forage crop. Kudzu’s heyday came in the late 30s and 40s when popular media outlets loudly promoted the vines as a “miraculous” nitrogenous gift to cotton-gutted southern soils. Largely through subsequent efforts of the Soil Conservation Service and the Civilian Conservation Core, kudzu was planted widely until the early 1950s when sanctioned plantings finally ceased.
Despite extensive management efforts, kudzu now covers up to 8 million acres in the eastern US from Florida to New York. Once believed to be problematic only in mild climates, kudzu’s impacts could increase in mid-Atlantic and northern states as winters warm and growing seasons lengthen. Kudzu now commonly overwinters in Maryland; in the past, during more consistently cold winters, it did not survive.
The most important environmental impact of kudzu is its devastation of local biodiversity. However, kudzu may also help degrade local air quality by emitting large amounts of the small hydrocarbon isoprene, which reacts in sunlight to form ozone. Soils infested with kudzu also emit nitrogen-containing compounds that have been linked to ozone formation. In addition, kudzu plants can serve as alternate hosts for the pathogen soybean rust.
Fitting with its controversial history, kudzu has as many uses as it does deleterious environmental effects. In Japan, kudzu is cultivated for fiber and for the high-quality edible starch in its roots. Kudzu extracts play an important role in many Chinese and herbal remedies and have been found to be effective against alcoholism. Perhaps most ntriguingly, kudzu could produce as much bioethanol per acre as corn. If harvested economically, kudzu-derived biofuel could help finance the reclamation of land already infested with kudzu. That said, the use of kudzu crops as a sustained source of biofuel would be ill-advised barring substantial advances in kudzu control and management techniques.
Control efforts range from repeated mowing to grazing with herds of sheep or goats, to the laborious application of herbicides to individual crowns. Biocontrols are being developed, with one fungal pathogen being recently patented for use on kudzu. Perhaps the most effective control of kudzu, however, is to prevent its establishment in the first place. This could be accomplished through inspections of soils and vehicles, by discouraging the sale and transport of kudzu, and by digging up any new plants before they get established.
For more information about other Invasive Species of Concern, visit www.mdinvasives.org or call the Maryland Department of Agriculture at 410-841-5920.
For more information on the Internet:
Kudzu Biological Control of Invasive Plants in the Eastern United States, invasive.org