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Origin
Humulus japonicus was introduced to New England from Eastern Asia and was recorded as escaped as early as the late 19th century. Introduction was probably intentional but an exact reason is unknown.
Known Distribution
Japanese hops is found in all the states of New England, and ranges west to Michigan and south to Virginia and Missouri.
Habitat
Japanese hops grows in waste places, roadsides and fencerows. It can also be found in abandoned fields, particularly where soil is moist, such as river and stream banks or flood plains.
Ecology
Japanese Hops is an aggressive weed which may form dense stands capable of crowding out native plant species. Japanese hops is also capable of climbing trees and other vegetation resulting in shading and girdling.
Identification
Japanese hops is an annual vine in the hemp family (Cannabaceae) which can grow from 1.5 to 8 feet in length. Stems have downward pointing spines. The vine also produces tendrils.
Leaves, opposite, with 5 lobes and are 2-4 inches wide and up to 8 inches in length. The leaves are rough to the touch.
Flowers, fruits and seeds: Individual flowers are very small and have no petals. The green flowers occur in clusters which may reach 2 ˝ inches in length and bloom in early to mid-summer. Achene type seeds.
Dispersal: Seeds of Japanese hops are dispersed by mechanical means such as wind and water.
Prevention and Control: Pulling the plants at any time of year is effective, as long as the plants have not set seed. As much of the roots as possible should be removed. Pulled plants can reroot so care should be taken. When using herbicides, Roundup® is effective. Roundup® can be used at any time but is most effective July through September when the plant is most rapidly storing nutrients.
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