Japanese Knotweed

(Fallopia japonica)

Description: This plant has large, heart-shaped leaves and jointed, hollow stems that resemble bamboo shoots. Its ability to grow over six feet by summertime adds credence to being called “bamboo” by residents. They develop large clusters of white flowers by August, although they do not reproduce by seed.

Impact: Japanese knotweed grows so rapidly that they prevent just about anything else from growing near them. But the roots (rhizomes) are the real danger, as even a single splinter from the rhizome will regenerate the plant the following season. Shredding or composting dead knotweed, as well as driving over treated areas, can contribute to its spread throughout the Island.

Management: Management is possible, but will take multiple summers to reduce knotweed on your property to manageable levels. They key is reducing the plant’s storage of food in the root system. Cut or mow down plants in June to keep regrowth short. By August, apply foliar herbicides to reduce the plant’s ability to store energy in the winter. Plant material should be bagged or burned, not composted. Continue these steps each summer as you starve out the root system and create space for your plants.