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.
“We don’t know how Japanese hops got to the Root River; but now that it’s here, we need to work together with the public to control this invasive weed,” said Christina Basch, Noxious Weed Specialist at the MDA. “Since Japanese hops is a prohibited noxious weed on the state’s eradicate list, it’s important that we find infestations and work to get rid of it.”
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 email@example.com or 1-888-545-6684. It is helpful to include photos with the report. It is also important to report infestations other than those on the Root River.
Work is already underway to control Japanese hops in the Root River area. Through a grant from the MDA, the Fillmore Soil Water Conservation District and Houston County Planning and Zoning are conducting hops treatments on the Root River banks. Fillmore and Houston County officials, with grants from the Board of Water and Soil Resources Clean Water Fund, are also using Conservation Corps Minnesota (CCM) to control hops along the Root River Trail. The MDA is working with landowners and CCM to control hops on private lands. The MDA’s work to control Japanese hops and oversee the coordinated efforts is supported by the Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizens Commission on Minnesota Resources.
Images are available below. Please credit photos to the Minnesota Department of Agriculture.
Allen Sommerfeld, MDA Communications