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Japanese hops

japanese hops leaves

Japanese hops
Genus: Humulus
Species: 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.

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 (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 developed by the department.

Identification

japanese hopsLeaves: 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.

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.

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 by University of Wisconsin-Extension.

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