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  • Writer's pictureJen Haynes

Do you have knotweed in your yard?

There are four different types of knotweed in our province. Three of which have been found in the Boundary. In 2015 we found giant knotweed (fallopia sachalinensis) while doing a survey of the Kettle River. There are a number of sites of Japanese knotweed (Fallopia japonica) in our area but most of it is bohemian knotweed (Fallopia x bohemica).Bohemian knotweed is a hybrid of Japanese and giant knotweed. A lot of it is being grown in people’s yards and it is starting to escape. Knotweed is designated as Provincial Noxious which means you must control it. Knotweed can grow through asphalt and concrete. It can grow through foundation walls and come up through the floorboards and walls of your house. Knotweed is native to eastern Asia. It is also sometimes called false bamboo, but it is not a bamboo. The stems are hollow with reddish-brown speckles. The leaves are heart-shaped or triangle-shaped and bright green. It has creamy white flowers that grow in drooping clusters. Knotweeds can grow between 10 and 20 cm a day. Plants can reach a height of between 1.5 m to 6 m. Knotweed spreads primarily by underground rhizomes. The roots can spread 20 meters laterally and 3 meters deep. They can grow from root fragments which can remain dormant in the soil for years. Knotweeds are difficult to control. They have extensive root systems that can sprout even after many years of control. Cutting them down is not effective. It stimulates the roots to spread farther when you cut it. You can dig it out, but you would need a machine to dig it and the material would need to be buried extremely deeply to keep it from growing. The most effective and efficient way to kill it is with herbicide. The best option is to hire a spray contractor to treat your knotweed for you. For more information on treating, it yourself or which contractors are available in your area please contact us. It can take several years to gain full control and you will need to continually monitor to see if it comes back. Do not compost knotweed as your compost will not get hot enough to kill it. If you cut it, you need to double bag it and take it to the landfill to be buried. Please do not share this plant with friends! Native alternatives would include oceanspray, Saskatoon berry and black elderberry. For more information please contact the Boundary Invasive Species Society at 250-446-2232, on Facebook, or check out our website .

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