Japanese Knotweed is infamous for invading, conquering, and taking over large swaths of ground, replacing the native vegetation with impenetrable stalks of "cane" that can easily grow twelve feet tall. Here's a patch measuring about 50 ft x 50 ft (and spreading), located near the trailhead for Nells Rock Trail, off Nells Rock Road in Shelton. According to Wikipedia, its roots can spread out up to 23 feet and go down up to 10 feet.
Once established, it is nearly impossible to eradicate. People have tried herbicide spray, digging it up, and covering it with sheets of plastic, with poor results. Instead, it is necessary to inject concentrated herbicide into the hollow stems, and they've even invented a tool for this: the JK Injection Tool, said to be 98% effective. This is the best time of year for that (the poison is drawn down into the roots), and so I spent a couple hours one morning attacking the patch at Nells Rock. I used a Sharpie to mark which canes had been injected. Only the canes that are injected will die. So each stem must be injected.
Here's a clue as to where the Knotweed came from. The plant was growing out of piles of gravel yard scrapings that had been dumped here long ago. The Knotweed had come along for the ride.
It's most efficient to attack small clumps before they become established, so I targeted this new patch along Hope Lake and the Rec Path. There were a total of only eight stems to inject. Hopefully those Knotweed plants are gone for good. We'll find out next year.
Here's another small patch growing along Hope Lake and Nells Rock Road. This patch is more of a problem since there are lots of small stems. The injector tool doesn't work on small stems -- it just splits them open. So I'll need another plan of attack for this clump.
Future projects: The Bluff Walk at Riverview Park is currently routed onto pavement at the basketball courts because there is a huge stand of Knotweed in the way (above). If I can kill off that Knotweed, we can get the trail off of the pavement. That's a big project, however, possibly for 2011. There is also Knotweed overrunning native wildflower areas at Birchbank Mountain, and some relatively new patches along the Blue Trail near Constitution Blvd North.