P&PDL Picture of the Week for
February 13, 2006

Japanese Hops (Humulus japonicus) - One of Indiana Rising Problematic Weeds

Glenn Nice, Weed Diagnostician, Department of Botany & Plant Pathology, Purdue University

When one thinks of hops they generally think of the beverage created from its cousin H. lupulus, but when a weed scientist thinks of Japanese hops, all they think about is trouble.  Japanese hops is an aggressively growing vine that is considered an invasive plant in Indiana.  It can often be found along ditches or creek banks because of it affinity to moist soils.  This is also due to the fact that seeds are often dispersed by moving water.  It does best in full sun to partial shade and can sometimes be found infringing on pastures, roadsides, and open fields. 

This vine has simple, opposite leaves with 5 to 9 distinct lobes.  In most cases that I have come across in Indiana, plants have had only 5 lobes.  Leaves are on long petioles and have erose or toothed margins.  The leaves are rough to the touch.  There are bracts, small leaf like structures, at the base of the petioles.  Stems are also rough to the touch due to down pointing hairs/prickles.  Flowers are inconspicuous and green and are born on leaf axils.

Control options are limited to hand pulling before the vines produce seed.  Spot applications of a glyphosate product just before flowering is reported to have some effect.  In ‘Invasive Plants of the Upper Midwest an Illustrated Guide to Their Identification and Control’ by Elizabeth J. Czarapata (2005) she mentions a cut-stem treatment with glyphosate between July and September may be effective.  However, there is very little research that I could find regarding Japanese hops control.

Picture source: Virginia Tech Weed Identification Guide

 

Click image to enlarge

Japanese hops (Humulus japonicus)

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service