Saturday, April 24, 2010

Japanese Knotweed

Sometimes, when I'm driving down the highway I look around at the roadside plants. Around here there is one plant in particular that crowds the roadside, the pond-sides, and forest-sides like eager shoppers pushing forward to be first in line on Black Friday. I speak of Japanese Knotweed (Fallopia japonica, syn. Polygonum cuspidatum, Reynoutria japonica), or what I like to call “Apocalypse Plant” because I imagine that someday when people are all gone, and there's no one here to pave roads, build buildings or weed gardens this plant will be all that's left. Japanese Knotweed is a tall herbaceous perennial that is native to Eastern Asia. I have been told it was a landscaping favorite of Fredrick Law Olmsted, a landscape architect who designed the Emerald Necklace in Boson and The Arnold Arboretum in Boston, New York City's Central park, and funnily, a monument in my very own town. Given his long list of accomplishments in the advancement of green space I won't hold it against him. But, it is listed by the World Conservation Union as one of the world's 100 worst invasive species. This plant is so vigorous that it will stand up to onslaughts of Round-Up, come up though pavement, grow through building foundations, and as I have witnessed stay alive and GROW from it's bare root when left out in a driveway for months. The roots can stay dormant for a long time and pop right back up when they are given a chance. A main plant can send it's horizontal rhizomes 25 feet and the root structure can go 9 feet deep.

It is basically impossible to kill. Years ago I lived next to this guy who had a back hoe come in and dig out his entire back yard and fill it with new soil. By the time I had moved in he was just getting his grass to grow. By mid-summer there was one shoot coming up tall and proud in the middle of his perfect lawn. He had told me his story and figured he had missed “one root.” I didn't know much about plants or invasives (actually, at the time I had a patch of mysterious plants show up and nearly pulled them out thinking they were this crazy weed, luckily I didn't because they were peonies!). Anyway, now I know that he could have dug up his lawn a million times, and the knotweed in the adjacent field would have continued to colonize his yard relentlessly. I don't know how he's doing with his battle, but I have started my own. I have a lovely garden of knotweed right on the boarder of my property. It's pretty big, with a few large “mother clusters.” It is spreading into my gardens and into my beautiful native bloodroot patch! Every year I have watched it come up and every year I halfheartedly pulled up a few plants where I want them the least. By early summer the whole area is completely filled in and I feel powerless against it all. It is edible and I have served it steamed to my family, but we found it tasted really not so good. Russ Cohen, a local edible food guru, swears by his knotweed pie recipe and claims no one has ever complained. I believe it, but I'm still getting rid of my plants come hell or high water! I figure if I get around to making that particular pie I will have a gazillion other sources to choose from.

So, I started to dig up all the individual plants that were growing onto my property. Much of the area I'm dealing with is rocky, which makes it really hard to get at. There are areas where the plant is coming up between huge boulders so all I can do is reach my arm into skunk-sized crevices between them and hope nothing bites be as I break off the pant. No good. I could get most of them up by simply shoveling them out. They actually pull up pretty easily, the trick is to get a lot of root. I did have to take an ax to one of the larger clusters, shown here, but I got as much of it as I could see.

Here it is almost completely dug out. You can see the giant root structure sitting on the rock.

So far I have spent three days pulling up this plant. I'd say I'm about half-way through. I have done so much that I actually feel hopeful. However, there must be a reason that no one suggests just pulling it out. The final word is always to kill it with poison, preferably to inject it directly into the root systems right before the flowering stage. But given my severe reluctance to use any kind of herbicide, I will try this first. I figure if I can keep on top of it and faithfully pull out every plant that comes up after making sure to take care of the most established plants I have to have a chance of eradicating it. Right?

As far as the plants I have pulled out, they are on a tarp in my driveway. I don't' even feel comfortable putting them in the trash and letting them get taken away to some far off landfill. So i am going to let them dry out and then burn them, I figure that ought to kill the jerks.

1 comment:

  1. Really hope this worked for you, but I've read in most places that pulling it up will actually form more plants, because every tiny root fragment you leave behind will form a new shoot. I am cutting off all of my knotweed stems at ground level and applying a drop of herbicide to the cut stem, and I will inject herbicide into the plant before it goes dormant in the late summer. Hoping in a few seasons it'll be gone. (Whatever happened to yours?)