Tag: leaves

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Japanese Hops Invading Southeast Minnesota

Japanese Hops
Japanese hops are an invasive weed that’s making its way into southeast Minnesota in the Root River valley. Minnesota Department of Ag officials are asking for the public’s help in identifying and controlling new infestations. (Photo from the Minnesota Department of Agriculture)

Japanese hops is and invasive weed that’s 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.

Infestations are popping up 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 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 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.

Japanese Hops
Here’s the difference between the invasive Japanese hops that are moving in on southeast
Minnesota and American hops. (Photo from the Minnesota Department of Agriculture)

Minnesota is also home to American hops. 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 they 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 arrest.the.pest@state.mn.us 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.

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Japanese Hops are MDA Weed of the Month

When you hear the word “hops,” you might think of beer. Hops are used in beer production to add bitter, floral, fruity, or citric flavors and essential oils for preservation. However, Japanese hops lack an essential resin for beer production. Common hops are a similar native species and can be used for beer production. Introduced to North America as ornamental vines, they are native to eastern Asia. Unfortunately, Japanese hops escaped cultivation and have become invasive.

Japanese Hops
Japanese hops form a dense mat and can choke out other plants. (Contributed Photo)

Japanese hops have distinct bracts where the leaf and petiole attach to the stem. The leaves have toothed edges with 5 to 9 lobes arranged palmately (shaped like a hand with fingers extended), while common hops only have up to 5 lobes.

The weed has both male and female vines. With female vines, seeds are produced in conical husks; male vines produce pollen from flowers. Hooked hairs on the stem and leaves help the vines climb but can irritate human skin after contact.

Seeds from the vine are easily dispersed by wind, water, wildlife, vehicles, and equipment. This allows the invasive weed to grow very rapidly. In just one season, they can grow up to 35 feet long. The vines twine around to climb vegetation and structures, capable of smothering desirable vegetation and producing dense mats several feet thick.

Japanese hops have distinct bracts where the leaf and petiole attach to the stem. (Contributed Photo)

Japanese hops are annual vines in Minnesota but can be perennial in warmer climates. They thrive in partial to full sun including next to rivers, along roadsides, grasslands, and forest edges.

They’ve been found in southeastern Minnesota along the Root and Mississippi rivers, as well as in the city of Winona. Most infestations are on riverbanks and creep into adjacent forest understory.

If you suspect you have found Japanese hops, please take pictures of the plant, note the exact location, and send a report to arrest.the.pest@state.mn.us. If you have questions or would like more information, please visit the Minnesota Department of Agriculture or the Midwest Invasive Plant Network websites.