Learn / Ask The Landscape Professional
We have a new yard. Our grass was seeded last April. The grass is coming in and we have this weed that some people said cannot be killed. It is easy to pull up when small but once the plant gets larger, the root is very hard to get out of the ground. Can you please give us advice on how to get rid of this ugly and invading plant? Charley
Answer
What you are dealing with is Japanese
Knotweed, Fallopia japonica or Polygonumcuspidatum,
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 1800s as
an attractive ornamental planting. Once Japanese
Knotweed gets established it is virtually 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. Japanese
Knotweed 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
part of your property to another.
The stems are hollow and segmented and the leaves
and stems have a waxy coating to protect
from chemical sprays, so herbicides have a minor
effect on the plant. 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 bagged and put out in the garbage for
incineration, and 3) never put the removed plants
in your compost pile and never take them to a
public landfill; they will spread all over.
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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.
