Monday, May 21, 2012

Japanese Hops - No Good!

Here's another plant to watch out for. The Japanese Hop plant. Japanese hops is a dioecious, fast-growing, herbaceous annual vine in the Cannabinaceae family. Its leaves are simple, opposite, heart- shaped and palmately divided, usually into 5 lobes. Flowers are greenish and bloom mid to late summer. Green hops produced by female plants contain oval, yellowish brown seeds. The seeds are believed to remain viable in the soil for three years and are dispersed by wind and water along rivers and streams. The stems are 8-35 feet in length and are covered with rough hairs that are very irritating to bare skin.

Japanese hops can grow in sandy, loamy, clay, acid, neutral and basic soils. While it requires moist soil, it can growin semi-shade to no shade environments. It threatens open woodlands, fields, prairies and riparian corridors. It is widespread throughout the eastern United States and ranges from Maine south to Georgia and west to Kansas and Nebraska. In Indiana, most populations are in southern Indiana riparian areas, though a few northern sites have been reported.

This species is considered to be invasive and has a high reproductive rate, rapid growth rate, long range dispersal, and broad photosynthetic range. Japanese hops can form dense, almost solid, stands that outcompete native vegetation and has the potential to displace native riverbank and flood plain vegetation. Vines begin growth in May. Growth is rapid and the vines quickly climb over adjacent vegetation. By late summer, vines can be up to 35 feet in length, which can blanket nearby vegetation.

Plants can be hand pulled and removed from the area before seeds ripen. When pulling the plants, attempt to remove as much of the rootstock as possible. Long sleeves, pants, and gloves are essential to avoid skin irritation. It is likely that resprouts could occur from both the rootstock and the vines. An herbicide alternative is glyphosate (i.e. Roundup or Rodeo). Foliar application of glyphosate (mixed according to label directions) prior to flowering should damage the plant enough so it will not be able to flower and set seed. The seed bank is typically exhausted within approximately three years. Always read and follow pesticide label directions.

If you think you have Japanese hops growing in your yard, there are several things you can do.  However, I would highly recommend contacting an arborist and let them or a professional tree service that has a highly qualified plant health care division remove the Japanese hops for you.  Trees "R" Us, Inc. has 4 certifiied arborists on staff to help you with plant issues such as this.  Trees "R" Us, Inc.'s plant health care division is equipped with the right equipment, experience and personnel to complete the removal of your problem plants safely and accurately.  Contact us via the web at, or by phone at 847-913-9069, or email me directly at
Trees "R" Us, Inc. provides quality tree maintenance, expert tree care and comprehensive tree services to the north shore and suburbs of Chicago.  

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