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I have this plant in my yard that is spreading every year. What is it and what do i do to get rid of it?


What you are dealing with is Japanese Knotweed, Fallopia japonica or Polygonum cuspidatum, a terribly invasive plant that has swept across the majority of the US, Canada and UK. It is native to Eastern Asia and was brought here in the 1800's as an attractive ornamental planting. Once Japanese Knotweed gets established it is virtu- ally impossible to get rid of, but with hard work and vigilance you can successfully keep it under control.

Japanese Knotweed is a perennial that emerges from the ground in the spring and forms in large colonies created by the rapid growth of rhizomes which are underground stems. The above-ground colonies are generally so dense that you almost never see any other native plant because they are crowded out. It can grow 10 feet tall and has leaves that look like spades up to 5-6" long. The stems which grow annually and die back in the winter are bamboo-like and a reddish-brown color. Even though Japanese Knotweed doesn't reproduce by seeds, it can sprout from extremely small pieces of rhizomes left behind after you pull it out of the ground. Moving soil that has had Japanese Knotweed growing in it will spread it from one pan of your property to another. I've seen that in my own yard.

I have found that the best way of controlling Japanese Knotweed is to remove it as soon as you see it beginning to show up in an area, because once it's established it becomes much more difficult to remove. I use a combination of carefully pulling it up by the roots and then repeated cutting of the re-sprouts throughout the season. Eventually this method will greatly suppress the plant's natural photosynthesis process and deplete the rhizomes of their energy. Several cautions: 1) this is a long-term process that will require your persistence, 2) even the smallest piece of the plant will re-sprout so be very careful where you put the plants you remove. They must be burned; either at the regional incinerator or in your yard (check with your local officials to make sure you can do open burning where you live and make sure they are dried out before you burn them), and 3) never put the removed plants in your compost pile or take them to your public landfill, they will spread all over. Be patient and good luck!

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About Linda Lillie

Linda K. Lillie is the President of Sprigs & Twigs, Inc, the premier landscape design and maintenance, tree care, lawn care, stonework, and carpentry service provider in southeastern Connecticut since 1997. She is a graduate of Connecticut College in Botany, a Connecticut Master Gardener and a national award winning landscape designer for her landscape design and landscape installation work.


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