Japanese Knotweed-Invasive Woody Perennial


Should it be removed or nurtured?


Thank you for contacting the Toronto Master Gardeners.

Japanese Knotweed, Polygonum cuspidatum, or Fallopia japonica is one of the top ten invasive plants for Southern Ontario and GTA. Japanese Knotweed  is an aggressive semi woody perennial introduced to Canada in the 1800’s as an ornamental plant.

Japanese Knotweed spreads via huge underground roots (rhizomes), which can grow 2 metres deep and 15 metres horizontally away from the above ground clump of stems. These factors have to be taken into consideration when attempting to control it. If you wish to tackle this problem yourself, Ontario Invasive Plant Council recommends digging out the plant. “Digging young plants (including rhizomes) can eradicate new or early infestations. Japanese Knotweed has a large and dense root system and will quickly re-sprout when pulled or dug if the roots are not completely removed. Using a restoration plan with this method will prevent additional invasive species from becoming established in areas disturbed by digging/ pulling efforts.”

Do Not Compost. All plant materials should be placed in thick black plastic bags. Seal the bags tightly and leave them in direct sunlight for about a week before disposing of them to the landfill.

Once you have Japanese Knotweed under control the OIPC recommends planting out the area, or covering it in a thick layer of mulch, to reduce the chance of other invasive species moving in. Good luck with controlling this invasive plant!”

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