Apple #60: Kudzu

KUDZU

I just got back from a trip which involved driving through Kentucky. During this drive, I saw entire hillsides covered with a grayish mat of stuff. There was nothing living on these hills, just the gray, almost ashlike junk. Somebody else in the car said, "That's kudzu. It's killing everything in the South."

And then I saw that the gray stuff was vines, dead maybe from the winter, tangled and matted over everything, reaching up into trees until the trees had been choked to death, crawling along telephone wires until the wires were weighed down to the ground, just completely smothering everything. It looked similar to pictures I've seen of the devastation after a volcano: everything covered and destroyed by thick gray stuff.

• Kudzu is a perennial vine in the pea family.
• In the right climatic conditions (like that of the Southern US), it can grow as much as 20 meters in a season, or 30 centimeters per day.
• It is native to Japan and China. It was first introduced to the US in 1876 at a plant exhibition in Philadelphia. It was shown again at an exposition in New Orleans in 1883, after which people started planting it to provide additional shade for their porches or for decoration on trellises.
• In the early 20th century, people started using it for things beyond decoration, and here it started to get out of hand because the stuff took root in the ground. Mainly, people were using it as cheap supplemental feed for livestock that had over-grazed the land.
• The snake oil people got into it and started selling it as a "wonder plant" that could do all kinds of magical things. The Georgia railroad was handing out free kudzu plants, there was a Kudzu Club, kudzu became almost a cult.
• Then in the 1930's, the US government started planting it as a way to prevent soil erosion. This was maybe the source of the greatest damage of all. In an effort to stop erosion, which was part of the Great Depression at the time, the government handed out 84 million seedlings of kudzu. They gave farmers $20 per hectare of kudzu. By 1946, 1.2 million ha were planted with kudzu.
• Not too long after this, people started noticing that this plant was growing out of control. But it took a while before the wheels were set in motion to try to stop its progress. It wasn't until 1970 that the plant was designated as a common weed, and it was 1997 before the government called it a "noxious weed" in recognition of the damage it had caused.
• By the mid 1990s it had a "stranglehold" on an estimated 2.8 million ha and was spreading by 50,000 ha per year. So far, the only plants known to compete successfully with kudzu are other invasive species -- privet hedges and honeysuckle -- from China and Japan.

The good news is, people have found some ways to control kudzu:

• --Repeated mowing: this can weaken and ultimately control kudzu, but you need a pretty sturdy mower and blade to chop through the vines, which can be very thick and starchy.
• --Repeated grazing: this was one of kudzu's intial purposes in the US, and it does provide a good source of nutrition, and livestock like it. But you have to fence the area, give the livestock a big enough space to walk around in it, and you have to rotate the livestock to other types of feed.
• --Burning: I'm sure a lot of people would like nothing better than to light a torch to it, but it really only works if you burn in late winter or early spring. This limits erosion, and it also helps to expose the germinating seeds. And you also need to couple burning with an herbicide for it to be most effective.
• --Herbicide: This is the most common and most expensive option. Lots of different herbicides have been made, and most can be used in combination with grazing or burning. But some you have to be careful about getting it in a water supply, and most you also have to follow up with spot treatments for several years afterwards.
• --Persistence: The main recommendation I see over and over is to be persistent. As fast as this vine grows, and as ubiquitous as it has become, that is how persistent people have to be in fighting it back. And it's not just the vine that's responsible for the damage; it was also the ways people overused the vine that allowed it to get to where it is today. So we also have to change the ways we live and deal with it now.

Sources
Richard Blaustein, "Kudzu's invasion into Southern United States life and culture," from The Great Reshuffling: Human Dimensions of Invasive Species, The World Conservation Union, 2001
"Controlling Kudzu in CRP Stands," University of Georgia Warnell School of Forest Resources and College of Agricultural and Environmental Sciences
"Kudzu in Alabama: History, Uses and Control," ANR-65, Alabama Cooperative Extension Service, 1999