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May’s Work: Japanese Knotweed Mitigation

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Olmsted Parks Conservancy’s Team for Healthy Parks follows an annual plan for invasive plant management that prioritizes different species at different times of the year for the best outcome. May is a big month for Japanese Knotweed (Fallopia japonica.)

Japanese knotweed is a highly invasive plant species that poses a significant threat to native biodiversity – it can grow up to 8 feet per month in the early summer and will tower over people and young trees quickly!

The plant has bamboo-like stems that are hollow and segmented, with large, heart-shaped leaves arranged alternately along the stems. During the late summer and early fall, the plant produces clusters of small, white flowers. When our Team for Healthy Parks finds this plant, we add it to our maps and our annual knotweed eradication plan.

Japanese knotweed is so aggressive that rhizomes can push up through concrete and can stay alive for up to 20 years!  This means that once we begin treating an area, we’ll continue to monitor and be ready every year to prevent the spread of this invasive species and protect native biodiversity.

You can help us by volunteering, removing invasive species from your own yard, and reporting any new Japanese knotweed sites that you find in the iNaturalist app.

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