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Japanese hops

(Humulus japonicus)

Photo of Japanese hops
Photo credit: David Eagan

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

Other names for this plant include:
  • Scientific names: Humulus scandens
Ecological threat:
  • Invades floodplains, stream banks and lakeshores, where seeds can disperse via water.
  • The aggressive vine climbs over vegetation and trees.
  • When working with this plant, blisters and dermatitis can occur.
Overview map of Japanese hops classification in WI
Prohibited (red) and restricted (orange) counties

Classification in Wisconsin: Prohibited/Restricted (Prohibited/Restricted [Restricted in Buffalo, Crawford, Dane, Grant, Green, Iowa, Jackson, La Crosse, Lafayette, Monroe, Pepin, Richland, Sauk, Trempealeau and Vernon counties; Prohibited elsewhere)

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 [PDF] 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 the 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.

Stems: Annual, herbaceous vine up to 35 feet long with downward-pointing prickly hairs and no tendrils.

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. Native wild cucumber is 5-lobed but has tendrils and no prickly hairs on its stem.

Distribution

See the reported locations of Japanese hops in Wisconsin.

Do you know of additional populations? Send us a report.

Control

Mechanical: Hand pulling and removing plants before seeds ripen.

Chemical: Foliar spray with glyphosate can be used 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].
Links for more information: