Land Plants - invasive

Japanese Knotweed (Fallopia japonica) on Mar 28, 2022

Submitter has sample
EDRR Status: Local expert notified

Description of specimen

The knotweed occurs in an approximately 5 x 15 ft area in the northwest corner of our front yard, in a partially shaded area with other woody plants.


It's key to dispose of knotweed properly. It's notorious for sprouting...even a small piece of the stem lying on the ground can become a new plant. With this in mind, many ecologists suggest using herbicide to control knotweed because disposal can be difficult. If you attempt herbicide, it's possible that an over the counter glyphosate product like Round up may help. The fall is the best time to treat with herbicide because it translocates to the roots to kill the plant. A treatment in spring while the plant is small might be worth a shot if you're interested in trying this, but know that a fall treatment is still likely necessary.
All that said, it's common on residential properties to try a manual control. Feel free to pull and dig the plants and place them in a bag and then into the garbage rather than a yard debris bag or bin. Keep out of compost piles onsite. With manual work, keep an eye on the perimeter of the treatment area for about 20 feet to see if any new shoots pop up (sprout from lateral, underground roots). We don't have a program for treatment of knotweed locally unless you're right along a creek. Landscapers might be of help if you're not able to take care of this. Sincere thanks for taking care of this population before it spreads...knotweed is a very troublesome invasive weed. Michael Ahr, Benton SWCD

Michael Ahr
March 29, 2022, 5:23 a.m.