Humulus japonicus Siebold & Zucc.

Japanese hops

About plant names...

Japanese hops is native to temperate regions of eastern Asia—China, Japan, Korea, Taiwan and the Russian Federation—as well as to tropical Vietnam. It was probably imported for cultivation, but it escaped and spread quickly. It is related to the variety of hops, Humulus lupulus, used for flavoring and preserving beer, and may be used as a less suitable substitute for this purpose. Japanese hops is considered an invasive in Connecticut, Delaware, Indiana, Maryland, Pennsylvania, Virginia, and the District of Columbia.

Identification: This fast-growing vine has tiny hooks on its stems and leaves that allow it purchase on nearly anything it encounters, reaching between 3-20' (91-609 cm) in length. If you want to get technical, Japanese hops are bines, not vines: they climb with little hooks rather than wrapping tendrils around things like grapes, or using suckers like ivy. Stems are green or reddish purple, with ridges running along the length of the stem. Leaves are rough, with short hairs and 5-9 palmate lobes, and are 2-6" (5-15 cm) in size, with long petioles (stems). Plants are dioecious. Male plants have large cone-shaped panicles up to 10" (25 cm) long and 5" (12 cm) wide; female flowers are about 1" (2.5 cm) long. Though the panicles are large, the flowers are pale and unremarkable, each about ⅛" (3.2 mm) in size. They appear early to mid-summer.

Online References:

Humulus japonicus at Illinois Wildflowers

Humulus japonicus on

Humulus japonicus on the Plant Conservation Alliance’s Alien Plant Working Group Least Wanted List

Humulus japonicus on spes.vt.edu

Humulus japonicus on www.eddmaps.org

Humulus japonicus on Plants for a Future, a resource and information centre for edible and otherwise useful plants

Humulus japonicus on eFloras

References:

del Tredici, Peter, Wild Urban Plants of the Northeast: a Field Guide, Comstock Publishing Associates, a division of Cornell Universty Press, 2010, p. 288

7/20/2013 · Wooden Bridge, East Pepperell, Mass­a­chu­setts
≈ 11 × 7" (28 × 18 cm)

Male flowers. · 7/20/2013 · Wooden Bridge, East Pepperell, Mass­a­chu­setts
≈ 5 × 6" (13 × 13 cm)

9/1/2013 · Trail Near James River, Midlothian, Virginia
≈ 5 × 8" (13 × 19 cm)

Humulus japonicus description by Thomas H. Kent, last updated 25 May 2020.

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7/20/2013 · Wooden Bridge, East Pepperell, Mass­a­chu­setts
≈ 7 × 10" (16 × 25 cm)

7/20/2013 · Wooden Bridge, East Pepperell, Mass­a­chu­setts
≈ 9 × 6" (23 × 15 cm)

Male flowers. · 7/20/2013 · Wooden Bridge, East Pepperell, Mass­a­chu­setts
≈ 5 × 8" (13 × 20 cm)

9/1/2013 · Trail Near James River, Midlothian, Virginia
≈ 7 × 11" (18 × 28 cm)

7/12/2013 · Wooden Bridge, East Pepperell, Mass­a­chu­setts
≈ 24 × 16" (59 × 39 cm)

9/1/2013 · Trail Near James River, Midlothian, Virginia
≈ 15 × 10" (37 × 25 cm)

Male flowers. · 7/20/2013 · Wooden Bridge, East Pepperell, Mass­a­chu­setts
≈ 5 × 8" (12 × 19 cm)

Range:

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