KC Gardens

Japanese knotweed


Help! We have Japanese knotweed along our fenceline. We have tried cutting it back & digging it out & neither has worked. In fact, it’s spreading. I’m going to try round up but hear that even that and/or covering the soil with a tarp could take years to work. Any suggestions? What about the testing they’ve done on steaming it to death? Thank you! - Laura -


  1. 12 months ago

    Knotweeds are an annual pest. Control may require a multi pronged approach. Spraying with glyphosphate (Round Up) should take care of actively growing weeds. However, a pre- emergent weed control product may be necessary to prevent germination of future generations. Pre emergent control should be applied in November. Several products provide pre emergent control and may be safely used around lawn grasses. Among them are Barricade, Dimension, Gallery, Halts, Surflan and XL. Check the labels to make sure current formulas are still indicated as effective against knotweed. Steaming is probably not a practical approach for the home gardener As with most weed problems, persistence is the key.

    JoCo EMG

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