Japanese hops, Humulus japonicus, is overtaking the banks of the Root River in southeastern Minnesota and growing onto adjacent property.

Weed experts at the Minnesota Department of Agriculture (MDA) are asking for the public’s help in controlling the weed and reporting new finds.

Currently, infestations are found along the Root River from Preston to the confluence of the Mississippi River. Small infestations of Japanese hops have also popped up in Winona; however, these have been controlled.

Japanese hops are herbaceous, annual vines native to eastern Asia that can grow up to 35 feet in a single growing season. With this explosive growth, the vines smother native vegetation and even grow into trees. Leaves are approximately 2-6 inches long and have at least 5 lobes that are palmately arranged (shaped like a hand with the fingers extended). There are separate male and female plants that are beginning to flower this time of year. Seed production then follows.

Minnesota is also home to American hops, Humulus lupulus. It is a native perennial vine that looks similar but often has 1-5 lobes and does not have more than 5 lobes on the leaves.

For successful Japanese hops control, the dispersal of mature seed must be stopped. This can be done by pulling or cutting the vines at the base or with herbicide treatment. Herbicide treatment is the only practical approach for large infestations that can’t be mowed. Experimental torching of seedlings appears to be effective for control of small infestations.

If you find Japanese hops on your land and the infestation is beyond what you can manage, report it to the MDA’s Arrest the Pest line at arrest.the.pest@state.mn.us or 1-888-545-6684. It is helpful to include photos with the report.