The Q&A Archives: Japanese Knotweed /fallopia Japomica

Question: I bought a Fallopia japonica recently and have learned that the Nature Conservancy considers it an invasive non-native. Can I use this attractive plant without harming the environment? What is the best way to grow it so that it won't cause harm, or are its problems confined to waterside areas?

Answer: Japanese knotweed is one of those plants that has escaped cultivation and become a noxious weed in some parts of western Washington. Birds can transport seeds quite a distance, depositing them where they congregate; most often near bodies of water or in forested areas. When this happens, the plant can grow unchecked until it finally crowds out native vegetation. I suspect that it also travels when prunings are dumped in forested areas instead of being disposed of properly. Japanese knotweed is a lovely plant, and you can keep it under control in your own garden by pruning it back when it gets too large. Just be careful with the prunings - either lay them out in the sun until they are completely dead before disposal, or place them in a plastic bag and set it in the sun until the contents are cooked. As long as you're a responsible gardener, you should be able to enjoy your plant without adversely impacting the local ecosystem.

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