Humulus japonicus Siebold & Zucc.
Hemp family (Cannabaceae)
Origin: Temperate Asia (China, Japan, Korea, Taiwan and the Russian Federation) and tropical Asia (Vietnam)
Japanese hop was originally imported to the U.S. in the late 1800s for use as an Asian tonic and ornamental vine. It is still sold for these purposes today. Common hop (Humulus lupulus) contains bitter acids and essential oils used for flavoring and as preservative in beer. The chemistry of Japanese hop is less desirable for that purpose.
Chris Evans, River to River CWMA
Leslie J. Mehrhoff, Univ. of CT
Distribution and Habitat
Japanese hop occurs in scattered locations from Nebraska to Maine to Georgia and is most common in the Northeastern U.S. and eastern Canada. It has been reported to be invasive in natural areas in Connecticut, Delaware, Indiana, Maryland, Pennsylvania, Virginia, and the District of Columbia. Japanese hop prefers plentiful sunlight and moisture, rich exposed soil, and is most commonly found along stream banks and floodplains. Growth is less vigorous in shade and on drier soils, but it can grow in disturbed areas with fairly moist soils, including roadsides, old fields, and forest edges. In milder climates, it can survive the winter.
Japanese hop can spread to cover large areas of open ground or low vegetation including understory shrubs and small trees. Many thousands of hop plants per acre may be produced, eventually blanketing the land and vegetation. The vines grow rapidly during the summer, climbing up and over everything in their path and can form dense mats several feet deep, blocking light to plants underneath. Hop vines also twine around shrubs and trees causing them to break or fall over. It is invasive in riparian and floodplain habitats where it displaces native vegetation, prevents the emergence of new plants, and kills newly planted trees installed for streamside habitat restoration. Hop can quickly cover small trees hiding them from view, preventing mowing and obstructing herbicide applications.
Description and Biology
Prevention and Control
Do not purchase, plant or transplant this species. Vines can be hand-pulled wearing gloves, long-sleeves and long pants and shoes to avoid injury from the prickles. Systemic herbicides are most effective (see Control Options).
Native grapes (Vitis), Virginia creeper (Parthenocissus quinquefolia) and coral honeysuckle (Lonicera sempervirens).
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