ANNAPOLIS, MD (August 4, 2008)
Savior to scourge in only 7 inches a day
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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.mdinvasivesp.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
National Invasive Species Information Center (NISIC)
http://www.maxshores.com/kudzu/
