Knotweed round one


In Mexican Bamboo, I wrote about my preparations for eliminating the swale of Japanese knotweed in our front yard.

Now that it’s early June, it’s had 3-4 weeks to grow. Left alone, most of what is currently there would not grow much more. For the rest of the growing season, it would invest its growing energy in extending its territory. My main goal for this year is to prevent that.

The initial growth period uses up quite a bit of the energy & nutrients stored in the root network. So, I intentionally waited until it had grown to full size to maximize the resource drain before starting at it.

The backhoe is saving me lots of time pulling the stumps and breaking up the root system.
The backhoe is saving me lots of time pulling the stumps and breaking up the root system.

Over the next couple weeks, I’ll rip out all the large stumps and any large roots I can find in the process. This accomplishes 5 things:

  • It removes another chunk of the resources stored in the root network. This swale is well established so I’m estimating that the combined loss is going to be about 20% of the stored resources.
  • Although breaking up the root network means there are lots of pieces of root to grow over time, each piece has limited resources to grow a new plant making it easier to exhaust.
  • A secondary benefit of breaking up the root system is that the size of the shoot is an indicator of the size of the root. This makes it fairly easy to identify larger roots.
  • An established stump can replace a large stock in a few days but smaller shoots growing from buried roots can be cut off every couple weeks with a grass trimmer. The time involved in keeping it cut back is substantially less.
  • The knotweed invests its resources into regaining the “lost” territory instead of trying to extend it.
Current progress
Progress on the de-stumping as of yesterday. Tractor for scale.

Mexican Bamboo

Japanese Knotwood

Both the property in Miramichi and the one in Lakeville had a colony of Mexican Bamboo (or Japanese Knotweed). It’s a fast growing invasive species that is capable of killing off most vegetation that does not grow taller than it does.

I succeeded in killing it off on both properties. In both cases, it took 5 years. When I looked out of the window on our second viewing and saw it in front of the house, I chuckled. Having done it twice before I knew I could do it again & how long it was going to take.

When I was working away at it in Miramichi I did some Internet research. I found a site that explained why it was so difficult to kill off. The roots are brittle and are prone to breaking. The root system of the growing plants emit a chemical into the soil. So long as the chemical balance of the soil contains a certain level of the chemical, the broken off pieces of root remain dormant.

My guess is that the broken off roots only have a shelf life of a few years. If they don’t grow within 2-4 years they die. That means that if you can keep it from extending it’s root system for 3-4 years, the remaining roots in the soil die.

Even though the growing season is over, I got a head start on next year. The old stocks get in the way of cutting it back the next year’s growth. It doesn’t hurt that it improves the street view of the house.

After the Japanese Knotwood was cut back
View from the front after the Japanese Knotwood was cut back.