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Humulus scandens

Japanese hops

SunFull Sun – Part Shade

Overview

Humulus scandens is a fast-growing annual vine in the hemp family, climbing 6-35 ft (2-10 m) in one season by twining around supports. The square, green stems are covered in stiff, downward-hooked prickles that catch on clothing and can scratch or irritate skin on contact. Opposite leaves are rough-textured and palmately cut into 5-7 toothed lobes, 2-6 in (5-15 cm) across, on long bristly stalks. The species is dioecious: male plants carry loose, branched panicles of small greenish flowers, while female plants bear short, cone-like spikes of papery bracts. Flowering occurs from July to September, and the wind-borne pollen is a known hay-fever allergen. Each plant dies with frost, but a single vine sets abundant seed that germinates the next spring. Introduced from East Asia, it has naturalized along streambanks, floodplains, and disturbed ground in eastern North America, where it forms dense mats that smother low vegetation. It is regulated as a noxious or invasive weed in several U.S. states. Unlike the perennial common hop Humulus lupulus, it is annual and its female cones are not used in brewing.

Native Range

Humulus scandens is native to temperate East Asia, including China, Japan, Korea, and the Russian Far East. In North America it is an introduced species, naturalized across the eastern and midwestern United States and parts of Canada along rivers, floodplains, and disturbed sites.

Suggested Uses

Humulus scandens is not planted ornamentally in North America, where it is managed as an invasive weed rather than grown. In its native East Asian range it has a history of traditional medicinal use. Removal and containment are the typical aims wherever it appears in the region.

How to Identify

Humulus scandens is recognized by rough, square stems lined with downward-hooked prickles and opposite, palmately 5-7 lobed leaves with toothed margins. Male plants show branched sprays of tiny green flowers; female plants form short, cone-like bracted spikes. The annual habit and the abrasive, hooked prickles separate it from the perennial Humulus lupulus, whose leaves usually have 3-5 lobes.

Appearance

Size & Dimensions

Height6' - 35'

Width/Spread3' - 6'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~8 weeks

Summer Fall

Flowering runs from July to September, with male and female flowers on separate plants. Wind carries the pollen, which is a common late-summer allergen. Female spikes mature to dry, seed-bearing bracts by early autumn before the plant dies with frost.

Detailed Descriptions

Foliage Description

green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 4-10 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.5(Neutral)

357912

Soil Types

loam sand clay

Drainagemoist

Water & Climate

Water Needs

Medium

Care & Maintenance

Care Guide

Humulus scandens grows in full sun to part shade on moist, fertile soils and is most vigorous on riverbanks and floodplains with steady moisture. It germinates in spring, climbs rapidly, and completes its cycle in one growing season. The vine tolerates a wide pH range and average to wet soils but slows in dry, infertile ground. No winter care applies because frost kills the annual top. Contact with the hooked prickles can cause skin abrasion and irritation. Because it self-seeds heavily and overruns neighboring plants, its spread is difficult to contain once established.

Pruning

Formal pruning is not used for this annual vine. Cutting or mowing stems before the female spikes set seed in late summer reduces the following year's seedlings. Pulling young plants while small removes them before the prickly stems toughen.