Kudzu, the vine that never ate the South (2015)

2 years ago (smithsonianmag.com)

I grew up believing many of the myths that this article addresses. So I'm hesitant to believe it entirely without verifying additional sources. In particular, this quote seems misleading:

> the U.S. Forest Service reports that kudzu occupies, to some degree, about 227,000 acres of forestland

I quickly verified this statistic. But I know that "forestland" is a specific category of land. What about non-forestland? How many acres of kudzu are there on land that is not considered forestland?

> experts estimate that kudzu covers another 500,000 acres in the South’s cities and suburbs

I found this statistic about 500,000 acres quoted in several places, but didn't find which experts came up with that number. Still, it was very quick to find double the acreage in one specific type of non-forestland.

That doesn't even begin to touch non-forestland countryside (i.e. non-city, non-suburb)

The US Forest Service estimates that kudzu adds 2,500 acres each year. US Department of Agriculture estimates that it spreads by 150,000 acres per year. I don't think this is a discrepancy, just that each agency is looking at specific land types and uses.

It seems like this article is seriously cherry picking data to make it seem like kudzu is less of an issue.

  • Another thing is why is growth not exponential and is linear per year? That seems fishy as well.

Driving through dead forests covered in this vine on my way to PA from TX, I would respectfully disagree with their premise. When allowed to proliferate it strangled everything visible from the highway, and covered every inch of the hundreds of standing dead wood trees it had killed.

  • > everything visible from the highway,

    But isn't this exactly what the article is arguing?

    > As trees grew in the cleared lands near roadsides, kudzu rose with them. It appeared not to stop because there were no grazers to eat it back. But, in fact, it rarely penetrates deeply into a forest; it climbs well only in sunny areas on the forest edge and suffers in shade.

    > Still, along Southern roads, the blankets of untouched kudzu create famous spectacles.

    • Kudzu is an edge plant; it thrives in the boundaries between ecological zones. Where open land turns into forest you see it. Right there in the tangled thicket mass of bushes, shrubs, small trees and other vining plants. Deeper into the forest the canopy blocks more light and it opens up as the opportunistic, edge plants get shaded out.

  • Did it kill the trees, or did it proliferate after the trees died (and increased the direct sunlight reaching the ground)?

    • Kudzu does grow up and over live trees and kills them. It will also grow over abandoned buildings, or nearly anything really.

I have a constant battle with Kudzu every year. I wish we could find an easier way to kill the stuff, or transform it into something else.

That being said, goats will dig down and eat the hell out of the stuff.

I used to live in Maryland, and saw Kudzu do some impressive work. Acres of land are covered by one patch.

I now live in New York, and it's starting to show up here.

Fun times ahead...

  • I think the point of the article is that Kudzu isn't really a threat and hasn't taken over nearly as much as people perceive.

    • Numbers wise, sure, there are certainly more invasive species out there.

      The trick with Kudzu is that, unlike ligustrum sinense, it invades in a much more literal sense, covering both other plants and the ground itself as far as it can. It 'universally' impedes the growth of other plants, and arguably makes terrain less traversal (if only because it covers what's underneath).

    • It may not be an ecological danger, but it can be a pain. Yes, other vines can grow as quickly, but most of them have smaller leaves and less propensity to carpet entire areas. I think the visual impact may make it feel more impactful and lend to its mythologization.

  • Plant some Japanese knotweed next to it and watch them fight to the death!

    • I'll put up the oriental bittersweet that is slowly taking over and pulling down all my trees as a contender in that fight.

    • I think the knotweed will win.

      If I'm not mistaken, you can't sell a house, in the UK, if there's knotweed on the property.

A while ago someone posted an article about stacking and freezing farmed biomass. They wanted to sequester CO2 from whatever random stuff that could be farmed cheap and frozen in the winter by hosing it down and running pipes through it then opening or closing the pipes to make it either match the air temp or resist temperature change.

Large swaths of the south simply don't have winter. But how cold does it get and how far from wintery areas is it? Is trucking a bunch of kudzu an option?

  • This seems like an absurdly energy-intensive plan because you'd have to spend energy to maintain your mountain-sized pile .. which will heat itself up if it ever reaches warm enough to start decaying.

    The most viable farm based approach would be "reverse coal mine": make charcoal from the biomass by reduced-oxygen combustion, then put it all in the big pit you made when you dug up all that coal.

    However, there's no economic model for any of this, so carbon capture is never going to go beyond pilot schemes.

  • Unless your truck is using a carbon-neutral power source, then no it's not an option. You'll emit more carbon than you sequester.

    • Even ignoring that, dry wood is only around 50% carbon. I guess the soil mass is significantly more than that of the atmosphere, but I'd still want to fairly carefully verify we wouldn't be totally screwing something else up by also sequestering the other half of wood. Of course, we'd also have to decide where to place the new wooden mountain range.

    • I suspect some math is in order. A big truck can move a lot of carbon and I suspect there is some range within transport makes sense.

      edit - To clarify if a big diesel truck puts X CO2 into the air to move Y tons of CO2 some distance then clearly if X is greater than Y it just doesn't make sense. But, if X is 10% of Y for 200 miles then moving biomass 200 miles might make sense.

      Also the transport can be shrunk if the transport is electric. A diesel truck might dump less CO2 into the air than even a coal plant is dumping a ton of CO2 it might be dumping less (or more) per watt which might

In my calculus class in high school, one of the problems in the set at the end of the chapter about the rate of the growth of kudzu. None of us had heard of it (including the teacher), which I guess might be due to being in New England rather than somewhere it's more of a problem. I think I remember us thinking it was some sort of crop rather than a weed, so we were all very surprised at the super high rate of growth it used in the problem.

Does higher CO2 make it grow faster?

  • Not likely in any appreciable way like the conspiracy theorists are putting forward.

    I bet if you had lab controlled environments you could find some optimal level of CO2 for it to grow in if you could guarantee no pests or competitors. But those detractors will change with CO2 levels too. Also, beneficial things for the plant in question will change too, like other plants that fix soil nutrients and polinators. It is simply too complex of a question to truly know and tiny changes in a superficially positive direction could have wildly unexpected negative impacts from an unmodeled directions.

    So... I don't know and I doubt anyone does unless they have studied the whole ecosystem for a long time.