Knotweed Project Info

FoAGM made a proposal to the Lexington Conservation Commission in 2004 to eradicate the Japanese Knotweed along a 100 foot section of the Minuteman Bike path. After some research two experimental methods were started in April 2005. One method is repeated cutting of the plant. The second is to dig up the rhizomes and cover the area with black plastic. The following are the reports of several FoAGM members who have worked on the project. Additional volunteers for any size time commitments are most appreciated. For information on how to help out contact Mike Tabaczynski at mjt1@rcn.com.

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To bring everyone up to date on our project, we assembled a crew of six on Columbus Day and pulled most of the JKW out of our “cut, cut, cut” area (to the east of the mid-section planted in grass). Not all of it could be uprooted, but I would say that 75-80% of the plants came up with at least 3-4” of root mass, in some cases much more. About 10% of these uprooted plants showed visible signs of the white fungus I documented earlier. Where the plant could not be uprooted, we simply broke off the stems at ground level. The removed plants were left in piles on-site to compost. There are obviously still root masses and rhizomes deeper underground from which the uprooted plants were growing. It is my educated guess, however, that the rhizomes won’t long survive, and that they will soon succumb in their entirety to the fungus and rotting process we have observed.
The plants which could not be uprooted, and which were broken off at stem-level, will certainly continue to generate plant growth next year, but I expect it will be at a much-reduced level. The plan will be to continue to cut these plants periodically, with the expectation that they will eventually succumb to the same fate as the rest. If this “cut, cut, cut” methodology does prove to be successful, we may attempt to continue the eradication eastward down the bikeway. The goal would be to accomplish the maximum destruction of JKW with a minimum of effort and investment. - JB

      In case this didn’t sink in the first time, let me try again. We really seem to be at a turning point on the JKW project!
      I stopped by at the site again yesterday evening and reconfirmed what I had experienced the week before. On the east side of the grassy area, it is now possible to remove much of the JKW (about 60-70%) that has been subjected to repeated cutting simply by giving a firm grasp to the plant close to the ground and pulling it up in its entirety, roots and all. Significant chunks of rhizome come out with the plant. In about a half-hour, I was able to clear out as stretch of bank about ten feet wide and almost all the way down to the bottom of the bank. Again, I added significantly to the waste pile.
      I bet we could easily clear out most of the bank this fall. I suppose I can do all the pulling by myself, a little at a time, but if anyone else wants to join me or give it a try on their own, the help would be welcome. If enough native plants grow in to hold the soil, it won’t be necessary to plant special grass.
      I haven’t tested the JKW on the west side of the grassy area, but since that has been repeatedly cut also, albeit by a different method, it might be in a similarly weak condition. - JB

     I am pleased to report, based on a couple of evening visits to the JKW site this week, that the “cut, cut, cut” method finally seems to be producing some very positive and encouraging results.
     Focusing on the area at the top of the bank between the area we reseeded two years ago and the waste pile, I found that with relatively little effort I was able to pull up by the roots a number of the JKW plants that had re-sprouted since our last cutting in early August (ranging from about 6” to a couple of feet in height). For about 50-60% of the plants, a reasonably solid tug brought up not just the stalk but also five to eight inches of very weakly rooted root or rhizome mass. The remainder of the plants remain more solidly rooted and can only be broken off at the surface. In the space of about a half-hour each time, I was able to clear out a very substantial quantity of JKW plants and add significantly to the waste pile. (Warning: The waste pile contains a sizeable hornets’ nest, so don’t get too close.)
     Clearly, the repeated cutting of the JKW drastically weakens the root systems. Although the rhizomes still have life in them, and the capacity to send up new shoots, they just don’t have the resiliency of those in a healthy plant. In many cases, you can actually see rotted and decaying rhizome masses and pieces of dead root in the ground. The relatively wet condition of the soil this fall (like last fall) also makes it easier to uproot the plants.
     To capitalize on this situation, I suggest we organize a “pulling party” later this fall, perhaps at the end of September or in early October, before the most recent growth dies back. I would bet that with three or four volunteers we could clear out most, if not all, of the area to the east of the plot in the middle that we re-planted with grass two years ago. If the 50-60% uprooting rate that I experienced at the top of the bank prevails farther down, there should still be enough JKW root systems left in the soil to prevent bank erosion, so I don’t think we need to worry about replanting this fall. We should have significantly less JKW in the area the next year, and I assume that other plants will naturally start to fill in the gaps.
    John B.

      As I had promised Don, I spent several hours at the site this past Sunday afternoon, focusing primarily on the eastern side. On the top, flat part of the bank, I pulled by hand virtually all of the JKW that was growing among the other weeds and wildflowers, which have become very thick now. I added quite a bit to the big pile on the corner. Reaching through the weeds and finding the JKW stalks can be a bit of a challenge. However, I was encouraged to find that over half of the stalks came up by the roots – in some cases fairly easily, and in others only with a strong two-fisted tug and a little back strain. The remainder were more deeply rooted and had to be snapped off.
      Where the JKW came up by the roots, the root systems seemed weak, a bit rotten and sometimes a bit mouldy, so I think our cut-cut-cut method really is showing some promise. The fact that the soil has been quite wet from the continuous rains probably did not hurt either. (In fact, in the middle of the work I was caught in a sudden, unexpected downpour, typical of this steamy and stormy summer, which I had to wait out in the trees for about twenty minutes.)
      After finishing off the top part of the bank, I weed-whacked the bottom part. Although the JKW there was not extremely tall, it was very thick and this was a strenuous job. Then, because the horseweed (I believe this is what Don calls it) at the top of the bank, about six feet high, was still blocking most of the view, I went ahead and chopped most of that down, leaving the wildflowers and the lower growth.
     I took a few photos showing the conditions before, and then stopped by again this morning, as Don, Sandra and Dave were finishing up their work on the west side, to get some “afters.” At some point when I have more time, I will try to cull out the best ones for possible addition to the web site. (One particularly good picture of Don is attached.) JB

With many hours of volunteer work the area has been cleared of JKW. But shoots continue to come up from the underground rhizomes and the area will require continued vigilance and work before the JKW can be said to be controlled. The picture below shows the view from the bikeway in 2004.

The area in AGM along the Eastern end of the Minuteman Bikeway has been heavily infested with Japanese Knotweed which has choked out all other vegetation and blocked what was once a very attractive view of the Meadows.

FoAGM Japanese Knotweed Control Project Information

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