Weed Watch: Japanese Knotweed
Japanese Knotweed blooming in late summer
This time of year you can see the tell-tale white blossoms of horribly invasive Japanese Knotweed (Fallopia japonica) and really get a picture of how wide spread it is, especially along waterways.
This invasive plant was brought to this country in the late 1800’s as an ornamental plant and began its march across the East coast. These plants create thickets that exclude all other plant life. They can grow 11 feet tall and pretty much continuously expand via underground rhizomes. Pieces of root or even stem easily propagate into new plants if they are disturbed or moved. It is now growing and expanding in 43 states.
Knotweed sprouting in spring -with triangular, reddish leaves.
The rhizomes are strong and grow very densely. They can force themselves through pavement cracks, wall mortar, floor boards and even harm building foundations.
Although it can tolerate many growing conditions, Japanese knotweed prefers moisture and tends to colonize wetlands and stream banks. Unfortunately, it is not particularly good at holding soil in place. During storm events, the roots allow soil to erode and often break off – creating new colonies where the roots come to rest downstream. The knotweed monoculture and soil erosion greatly degrade stream health.
Knotweed flowers
Controlling Japanese Knotweed depends on eliminating the underground rhizomes – which can be very difficult even with the use of herbicides. It requires persistence. If you have Japanese Knotweed on your property, you should address it as soon as possible. Be very mindful of transferring root fragments around the yard in soil. Never put roots in the compost and even stems should not be composted unless they are thoroughly dried first. The articles linked below have some strategies for containing and (hopefully!) eliminating knotweed.
Want more information? Here are some links:
Knotweed’s young growth with red tint