ST. PAUL, Minn. – State officials are issuing a warning about an invasive vine that is overtaking the banks of the Root River in southeastern Minnesota.
Infestations of Japanese hops, or Humulus japonicas, have been found from Preston to the Mississippi River growing from the riverbank and onto adjacent property. Small infestations have also popped up in Winona but the Minnesota Department of Agriculture (MDA) says they have been controlled.
“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.”
Experts say 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. The leaves are approximately 2-6 inches long and have at least 5 lobes that are shaped like a hand with the fingers extended. There are separate male and female plants that are beginning to flower this time of year.
The MDA says to control the growth of Japanese hops, the dispersal of mature seed must be stopped. That 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.
With state funding, 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.
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 firstname.lastname@example.org or 1-888-545-6684. It is helpful to include photos with the report and to report infestations other than those on the Root River.