getting rid of japanese knot weed

Asked July 24, 2014, 4:59 PM EDT

Hello, we have horse pastures in Columbia cty and need help in getting rid of this knot weed which is spreading thruout our fields, can you help us find a way to irradicate or control this invasive plant?

Columbia County Pennsylvania

1 Response


Thank you for contacting Delaware Cooperative Extension. You may receive a short survey after the answer to this question.
First, I would make sure you actually have Japanese knotweed by taking a specimen to your local County Extension office.

Japanese knotweed is an herbaceous perennial that can get quite large. It has hollow stems, alternate leaves, with green to white flowers. It can spread by seed, stem segments, and rhizomes. It grows in a variety of soil types and flowers in August and September. Seeds require light to germinate.

Control is best accomplished by removal of plants by digging or other mechanical means. Cautions should be used though, because new plants can start from pieces of stem and root left behind. Herbicides can help to eradicate. If using a glyphosate liquid solution, it should be a 2 % solution, not the dilute ready mixed product for sale. Herbicide treatment will probably require two applications, about 3 weeks apart, always apply to actively growing plants.

My best,