PPDL Picture of the Week

February 17, 2020

JAPANESE HOPS (Humulus japonicus) An Invasive Weed of Indiana​

Marcelo Zimmer, Weed Science Program Specialist

Department of Botany and 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 perennial vine that is considered an invasive plant in Indiana.  It can often be found along ditches or creek banks because of its 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 that are 2 to 4 inches long with 5 to 9 distinct lobes.  In most cases in Indiana, plants have only 5 lobes.  Leaves are on long petioles (up to 8 inches in length) 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 mostly limited to hand pulling before the vines produce seed.  However, spot applications of systemic herbicides containing active ingredients such as metsulfuron or glyphosate were shown to be the most effective at suppressing Japanese hops in trials from the DNR in Maryland.

 

Always read and follow all label directions when using herbicides.


Online resources:

Japanese Hops – Invasive Species Fact Sheet: https://www.in.gov/dnr/files/Japanese_Hops.pdf

Japanese Hop Images: https://www.weedimages.org/browse/subthumb.cfm?sub=10091

Managing Japanese Hops – What We Have Learned. https://dnr.maryland.gov/forests/Documents/jhopspresentation.pdf





Click image to enlarge


Picture source: Virginia Tech Weed Identification Guide