Thursday, July 9, 2015

Attack of the Knotweed - Birchbank Trail

Japanese Knotweed obliterates the trail in just a few weeks
I think we can all agree that Japanese Knotweed is evil.  It's an invasive species that shoots up quickly each spring, with canes reaching heights of 12 to 15 feet in a very short time, and over an inch in diameter. The roots can go down eight feet deep and come up through pavement. It's extremely tough to kill: When you cut it back it just shoots right back up again.  

Birchbank Trail runs through an ever expanding patch of the stuff, starting at the entrance and continuing 350 feet down the trail. The above photo of Birchbank Trail was taken in June. Since we have an intern this year, we decided to finally tackle the cancer that is knotweed. The first emergency step was to just clear a path, which intern Stephen did with hand pruners. People could now find the trail, but the knotweed starting growing back over the trail lightening fast, about a foot a week. So we decided to get the big gun: the brush cutter. The two photos below are a before and after of the exact same location:

Before using the brushcutter

Exact same location after removing the knotweed
Because knotweed grows as a colony, we decided to cut every shoot we could in the patch. Just cutting part of it is like trying to slay a giant by hacking at his toe. But even this will all be a waste of time if we don't follow up with repeated cutting to weaken the giant, followed by applications of Round-Up in late summer and fall when the plant begins to draw nutrient down out of the leaves and into the roots. Most of this plant is underground, so we need to starve it by repeated cutting.

While cutting, I discovered several native species hiding down below the tall canes of knotweed along the periphery, such as Jack-in-the-Pulpit and Trillium. While cutting the knotweed frees these natives from certain death by asphyxiation, they are now vulnerable to deer. One thing we plan to do is install a deer exclosure around a small area to demonstrate the impacts of deer.

UPDATE June 2016: The battle continues. Repeated cutting! Here's what the area looks like now:

June 2016. 

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