Learn / Ask The Landscape Professional
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?
Answer
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.
