Japanese Knotweed (alias Fallopia japonica)

Japanese Knotweed has invaded the entire mid- and lower Hudson Valley and well into Connecticut. It is found mostly along roadsides and water ways, where its seeds easily distribute the plant further downstream, crowding out indigenous plants all over southern New England and the mid-Atlantic.

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From a distance, Knotweed is very recognizable by its double edged swords, stacked up in layers.

If you want to see what Ulster and Dutchess County will look like in 10 years, drive along the Saw Mill Parkway in Yonkers, Dobb’s Ferry and Hastings on Hudson. The landscape there is completely covered with Knotweed and Grape Vines. The Little Delaware River in Delhi, NY is also covered, as well as the upper Esopus in Shandaken, NY, and the upper Rondout Creek in Accord, NY.

Learn about our all-natural methods for removing Japanese Knotweed and other invasives

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Looking closer, you can see the zig-zag of its stems and its pointed ovoid leaves

Characteristics: The mature root ball is about the size of a basketball. It is very dense and compact. Every spring, fresh new shoots emerge from the root ball. They are soft and brittle. Picking one up will cause it to break in two, and if that piece is left in the soil, you will have just created two new sprouts.

In the late summer, Knotweed flowers and in early fall, drops seeds every time it rains or the wind blows. The seeds will last 3 to 5 years in the soil before germinating. Knotweed has been known to go into dormancy for up to 20 years before reincarnating!

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Knotweed stems look like Bamboo.

Streams and creeks are super highways for knotweed stands, producing billions of seeds every fall. Rain washes the seeds into wetlands or rivers, carrying them further downstream. Along the way, they make it to roads where they are able to hitchhike on car tires further into the suburban landscape and into our yards.

Eradication: Knotweed is difficult to eradicate, but not impossible. There are two techniques available to us that will effectively wipe out the Knotweed. We can dig it up anytime from March to the end of August. If you don’t know what you’re doing you will spread the new shoots all over the place! We get the entire root ball and the shoots. This takes time and sweat.

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This photo taken in August shows the plant in peak flowering season.

Once a patch is dug up, it needs to be covered with landscaping fabric. After a few years, the new spouts will begin to pop up through the fabric as it disintegrates. At that point we’ll replace it with new fabric, dig up whatever has sprouted and put down new fabric. It could be safe at that point to cover the fabric with wood chips so it’s more attractive.

We have a special discounted rate for Knotweed so that it can be more affordable. Eradicating knotweed is a five-year commitment. If you have knotweed, it’s worth a conversation with us.

Learn how PI Patrol restores woodlands by removing invasive plants

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Beautiful, right? How many seeds do you see in this picture?

If you are unfortunate enough to have a huge stand of Knotweed, you may have to go to Plan B. That involves chemicals. The only time we would ever recommend using chemicals (or landscape fabric for that matter) is for Knotweed.

Poison Ivy Patrol does not do this work, but will recommend a licensed professional in your area. This is just as effective as digging it up, but it might be more affordable on larger patches. One thing is for certain, it won’t go away on its own.

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PI Patrol team removing knotweed in Red Hook, NY

In late summer, a professional injects Glyphosate (the active ingredient in Roundup) directly into every single shoot with a large syringe. During this time of year the plant is drawing nutrients from the flowers down to the roots to build food reserves before going into dormancy for the winter. The poison is sucked into the roots until it’s dead. Death by lethal injection!

Many people are opposed to chemicals, and it does have its drawbacks, but – it’s knotweed! And in this case, the herbicide is not sprayed. It is applied directly into the roots; not the surrounding soil. In time, it will leave no residue in the plant or surrounding areas.

Don’t do this yourself!!! There are many precautions, wetlands research, permits and restrictions that must be addressed before introducing poisonous chemicals into the environment.