Japanese Knotweed: The Focus of My Summer

In an earlier article, I alluded to a problem in our landscape.

Notice just left of the back porch (and left of the tree that was allowed to sprout up).  This photo doesn't convey the extent of this overgrowth, but it stretches in both directions for several yards.  At the time this photo was taken, it did have a rather pretty white bloom.  It was pretty enough that the landscape architect who completed drawings for our zoning application thought with a bit of a trim, the plant would make a nice backdrop to the landscape.

Seeing how overabundant the foliage was, we agressively cut back the dead stalks in the spring.  Each stalk seemed to resemble bamboo, and that find concerned us.  We dug up massive clumps of roots, each approximately 2 feet in diameter and weighing close to 30 pounds! 

It was apparent that several plants had been placed along the fence at some point to add some privacy and hide the aging fence.  Digging up these huge root clumps was difficult--okay, backbreaking--but once the task was finished, we felt very satisfied that we had tackled the problem.

Flash forward a few (not many!) weeks.  I look out the kitchen windows one morning and everywhere there are little red and green sprouts!  Time for some research!

That's when we tracked down the demon: Japanese Knotweed, one of the 10 most invasive plants on the face of the planet.  In some states it's banned, and I certainly wish it had been in Ohio.  I thought the plants were old, based on their size and amount of spread.  However, a couple months later the maintenance guy for the house next door told me that the former owner of our home planted it.  I could see the appeal, as it was likely labeled a fast grower, a great privacy screen with pretty summer blooms.  I get marketing.

Research told me that even the tiniest piece of live root or stalk would result in more growth.  And the pieces are so friable that it is nearly impossible to pick them up without breaking them.

So began the war. 

I sprayed them with Round-Up on my side of the fence.  It took 2 treatments per plant for a total kill, but new shoots persisted. I wasn't just fighting the battle on our side of the fence.  This plant certainly doesn't understand boundaries, so the neighboring landscape was totally infested.  There, spraying was difficult due to the extensive landscaping.  So I used syringes to inject Round-Up into the stalks and to spray in a more controlled fashion onto leaves.  Satisfaction over many plants killed and removed was always followed by new little shoots a few days later, happily bobbing in the breeze.  By the end of the summer, I saw the bobbing leaves as little tongues giving me the raspberries.

It's winter now.  All signs of knotweed are gone.  I know the spring will bring a resurgence, but how much?  Research told us with diligence we might conquer the beast in 7 years.  I am hoping we were ultra-diligent and will see significantly less of the stuff this spring.  Fingers crossed.