knotweed

Photo of Japanese knotweed from Cornell University Cooperative Extension.

By Ruth Seward
Director Outreach & Community Engagement

When I work in the community landscape, watch for signs of invasive plants. The USDA’s definition of an invasive species is “Non-native (or alien) to the ecosystem under consideration; and, whose introduction causes or is likely to cause economic or environmental harm or harm to human health.” The invasive plants I encounter are fast growing and difficult to remove from the environment therefore they can easily eliminate other plants from a greenspace.  

Two plants I look out for include Japanese Knotweed and Oriental Bittersweet. Knotweed, sometimes referred to as ‘Bamboo’ is extremely difficult to eradicate from the landscape. It spreads less by its seeds and more by its underground stems (rhizomes), above ground stems and crown. Methods used to curtail its growth include cutting new spring growth back and smothering the plant with a large tarp, cutting back the stem growth in the summer and digging up the root system. People apply herbicide to the plant in the fall, but I prefer to cut the stalks and fill with salt for a less toxic solution.   

Oriental Bittersweet, different than the native American bittersweet, also spreads rapidly underground. This is a vine that will grow along trees and woody plants, eventually either strangulating the host or blocking sunlight from leaves. Herbicides can be applied to the leaves and stems of this plant. I prefer to remove it from the plant it is invading, then pull the roots from the ground since they usually are easy to