Japanese hops

Japanese hops (Humulus japonicus)

Climbing annual, herbaceous vine that grows up to 8’. Downward pointing, rough hairs on stems and leaves aid in twining clockwise on nearby vegetation. Stems are light green to reddish in color.

Overview

Regulated areas of Japanese hops
Japanese hops is Prohibited (Red counties) and Restricted (Orange counties)

Other names for this plant include:

  • Scientific names: Humulus scandens

Ecological threat:

  • Invades floodplains, stream banks and lakeshores, where seeds can disperse via water
  • Aggressive vine climbs over vegetation and trees.
  • When working with this plant, blisters and dermatitis can occur.

Classification in Wisconsin: Prohibited/Restricted

Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for Japanese hops was based upon this literature review developed by the department.

Identification

Leaves: Opposite, 2-5” long, with serrated edges and palmately divided into 5 or more lobes. Petioles are as long as or longer than length of leaves.

Flowers: Originate in leaf axils, are dull green with 5 petals on spikes. Male and female flowers are on separate plants. Male flowers are upright while female flower clusters droop and bloom from July-September.

Fruits & seeds: Achenes are yellow-brown in color. Seeds can be dispersed by wind and water.

Similar species: Native hops (H. lupulus) have 3-lobed leaves with petioles shorter than the length of the leaf.

Distribution

Known county distribution of Japanese hops
Counties in WI where Japanese hops has been reported (as of July 2011). Both vouchered and unvouchered reports included.

Do you have Japanese hops in your county but it isn't shaded on the map? Send us a report.

Control

Mechanical: Hand pulling and removing plants before seeds ripen.

Chemical: Foliar spray with glyphosate can be used at before flowering.

For more information on control techniques, visit the Japanese Hops factsheet [exit DNR] by University of Wisconsin-Extension.

Photos

View Japanese hops pictures in our photo gallery!

Resources

Sources for content:

  • Czarapata, Elizabeth; Invasive Plants of the Upper Midwest: an illustrated guide to their identification and control. University of Wisconsin Press. 2005. Pg. 128-129
  • Center for Invasive Species and Ecosystem Health: Invasive.org. Last updated on May 04, 2010. Japanese hops [exit DNR].
  • Robert W. Freckmann Herbarium. University of Wisconsin-Stevens Point. Humulus japonicus [exit DNR].

Links for More Information

Last revised: Wednesday June 05 2013