Thursday, January 21, 2010

Hedera helix

Well, it's been cold lately in New York. The past few days we finally broke into weather above 35° and it felt downright tropical (if only). Add this to the fact that I'm planning a big move and packing and well, at least for the time being, I have a full time job, so it's safe to say I've been awfully busy.

But that doesn't mean I can't post something up here. Even if it's as plebeian as English ivy (Hedera helix), seen here growing up Platanus x. acerifolia at the Marble Cemetery.

Everyone knows this plant. Over the past five years of teaching, very few students are unable to identify this plant as ivy when encountered with it. It's a very handy, practically-bulletproof plant that can be used as a climbing vine (as above) or as a groundcover (as below).

But there are probably things about Hedera helix that the average person doesn't know.

The name itself comes to mind. Hedera is simply the Latin name for ivy, but helix tells one more about the plant. Specifically that the leaves emerge from the stem in a helical pattern (much like the way DNA molecules are arranged in a strand).

Above you see the more recognizable form of ivy climbing the wall, then it balloons out into a shrub-like mass and starts to fall back down the wall. That's the adult phase of the plant. The form we see most often is the juvenile stage.

Here's ivy, in adult form, climbing a tree at Liz Christy Garden. The overall form of the plant isn't the only thing that changes. If you look more closely, you see the leaf changes from a three-lobed shape into a more ovate-shaped leaf - the lobes disappear.

You also see that, like people, this plant is able to reproduce once it is in the adult stage. Bluish berries fruit a year after minute flowers are pollinated. These fruits are mildly toxic.

The next obvious question is, why can some ivy plants remain at the juvenile stage for decades, while others enter the adult phase? The key is height. Generally, when the plant is more than 20 feet above-ground, and it is not being pruned or clipped, it enters the adult phase.


How It Grows said...

I was reading that it's actually Hedera hibernica that is running rampant in Virginia, but haven't come across any tips on distinguishing it from H. helix. Any tips?

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Anonymous said...

From Virginia, so, I noticed, no blog about Kudzu, here is a favorite, "the vine that ate the south."

Kudzu is sometimes called gé gēn[1] (Chinese: 葛根), and (due to its out-of-control growth in the Southeastern United States) has earned such pejorative nicknames as the "foot-a-night vine", "mile-a-minute vine"[1], and "the vine that ate the South" (of the United States).[2]