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Ivy: It’s On the Rise

November 2, 2010

It’s getting a little late in the year for this post, but let’s think of it as a fond farewell to summer weeding (not that I still don’t have plenty of weeding left, but boy ivy slows down once it gets cold!).

I hate English ivy. I know, I know — it looks beautiful when draped majestically over an old English manor house, but really, it just doesn’t belong here. Like so many other plants that are considered invasive in this country, English ivy was imported as a landscape plant, and of course is still used in many backyards.

Can you spot the ivy?

But maybe we should take a step back and define “invasive” in this context. Many people equate invasive with non-native species. While it’s true that invasive species are generally not native, not all non-native species are invasive. When a plant (or animal) is let loose onto a “naive” ecosystem (one which hasn’t yet been exposed to that particular organism), the plants and animals that make up that system might not have defense capabilities against the new species, as they didn’t evolve together. On the other hand, a non-native species might be benign and not out-compete or over-eat the native species (a good example of this would be our feral pigeons).

So back to ivy. The stuff grows like crazy around DC, and is really hard to get rid of once it’s established. It crawls up flowers, bushes, and trees, and if left unchecked can basically strangle what it’s growing on (granted, it’s nothing like kudzu, but then again we don’t have kudzu in our backyard!). Can you tell how much I dislike the stuff?

Here’s the rub: It turns out that the increasing amount of carbon dioxide in our atmosphere is also causing vines (such as English ivy) to increase their growth rate. One study showed that when they artificially increased carbon dioxide levels from 365ppm to 660ppm, ivy biomass doubled and stem length increased by a whooping 137% (Moore 2004)! Granted, we’re (hopefully) not going to be anywhere near 660ppm anytime soon, but we’re already over 365ppm. So it’s not just me — the stuff is growing faster than it used to!

What about now?

Here’s a nice recent Post article describing what to do with invasive vines, and here’s the United States National Arboretum’s (located right here in DC) invasive plant page.

 

 

Moore, P.D. 2004. Plant ecology: Favored aliens for the future. Nature 427: 594.


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