Appearance
Humulus japonicus is an annual, climbing, or trailing vine that is native to eastern Asia. This vine has 5-lobed leaves (generally), downward-pointing prickles on the stem, and bracts at the base of the petioles.

Foliage
Leaves are opposite, rough, 2-5 in. (5-13 cm) long, 5-9 lobed with toothed margins. Most leaves will have five lobes, but the upper leaves may only have three.

Flowers
Flowers originate in the leaf axils and are green with five petals. Male and female flowers occur on separate plants (dioecious). Female flowers occur in cone-shaped clusters that hang down and the male flowers occur in upright flower stems.

Fruit
Fruit is a yellow-brown ovoid achene. The small seeds are distributed by wind and water.

Ecological Threat
These vines can grow to 35 ft. (10.7 m) in one growing season, allowing them to infest large areas crowding and out-competing native vegetation. Humulus japonicus was introduced into North America in the mid-to-late 1800s as an ornamental.

Resources

• Weed of the Week - USDA Forest Service
• Weeds Gone Wild Fact Sheet - Plant Conservation Alliance, Alien Plant Working Group
• Plant Invaders of Mid-Atlantic Natural Areas - National Park Service

Selected Images

Maps

Invasive Listing Sources

• Connecticut Invasive Plant List
• Connecticut Invasive Plant Working Group
• Delaware Invasive Species Council
• Indiana Invasive Species Council - Invasive Plant List
• Indiana Terrestrial Plant Rule
• Invasive Plant Species of West Virginia
• Jil M. Swearingen, Survey of invasive plants occurring on National Park Service lands, 2000-2007
• John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995.
• Kentucky Exotic Pest Plant Council - Significant Threat
• Maryland Department of Agriculture's Candidates for Listing of Invasive Plants
• Maryland Department of Natural Resources Policy: Restriction on Planting Exotic Invasive Plants
• Maryland Invasive Species Council - Invasive Species of Concern in Maryland
• Massachusetts Invasive Plants Advisory Group List
• Massachusetts Noxious Weeds
• Massachusetts Prohibited Plant List
• Mid-Atlantic Field Guide to Aquatic Invasive Species
• Minnesota Noxious Weeds
• Missouri SRISP Species List
• National Park Service, Mid-Atlantic Exotic Plant Management Team Invasive Plant List
• New Hampshire Invasive Species Committee. 2005. Guide to Invasive Upland Plant Species in New Hampshire. New Hampshire Department of Agriculture,  Markets and Food Plant Industry Division and New Hampshire Invasive Species Committee.
• New Jersey Invasive Species Management Act
• New Jersey Invasive Species Strike Team 2017 Invasive Species List
• New York Regulated and Prohibited Invasive Species - Prohibited
• Non-Native Invasive Plants of Arlington County, Virginia
• Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
• Pennsylvania Department of Conservation and Natural Resources Invasive Plants
• Pennsylvania Noxious Weeds
• Pennsylvania's Field Guide to Aquatic Invasive Species
• Plant Invaders of Mid-Atlantic Natural Areas
• South Carolina Invasive Pest Council
• Tennessee Exotic Pest Plant Council
• Virginia Invasive Plant Species List
• WeedUS - Database of Plants Invading Natural Areas in the United States
• West Virginia Native Plant Society, Flora West Virginia Project, and West Virginia Curatorial Database System, September 3, 1999
• Wisconsin's Invasive species rule – NR 40

References