COMMON NAME

Japanese hops


FULL SCIENTIFIC NAME

Humulus japonicus Sieb. & Zucc L.


FAMILY NAME COMMON

Hemp family


FAMILY SCIENTIFIC NAME

Cannabaceae


IMAGES


Leaves and Inflorescences

Fruits Close-up

Habit

Habitat

Climbing Habit

NOMENCLATURE/SYNONYMS

Synonyms: Humulus scandens auct. non (Lour.) Merr.


DESCRIPTION

Botanical Glossary

Humulus japonicus is a monoecious, annual vine that can grow between 0.5-2.5 m (1.5-8 ft.) in length. The stems and leaves of this plant have a very rough texture. The leaves are cordate in outline and palmately lobed. The leaves have 5 to 9 lobes separated by V-shaped sinuses. The margins of the lobes are serrulate and they have an acuminate apex. The leaves measure 5-12 cm (2-4.75 in.) in length, and the petiole is often longer than the leaf blade itself. The uppermost leaves are often 3-5 lobed.

The staminate inflorescences are erect and measure 15-25 cm (6-10 in.) in length, while the pistilate inflorescences are cone-shaped spikes, 7-10 mm (0.25-0.4 in.) in size and the margins of the bracteoles are densely ciliate. The pistilate spikes are dull green in color and become abruptly acuminate. The flowers bloom in early to mid-summer. The achenes are yellow-brown, ovoid-orbicular in shape, and 4-5 mm (0.2 in.) in length. Page References Bailey 341, Fernald 556, Flora of North America 384, Gleason & Cronquist 73, Holmgren 70, Magee & Ahles 421. See reference section below for full citations.


SIMILAR SPECIES

Humulus lupulus L. (Common hops)

Character Humulus japonicus Humulus lupulus
Life cycle Annual Perennial
Leaf lobes 5-9 lobes 3-7 lobed, sometimes unlobed
Apex of leaf lobes Acuminate Rounded
Petiole Longer than the blade Shorter than the blade
Bracteoles of pistilate spike Ciliate Not ciliate

REPRODUCTIVE/DISPERSAL MECHANISMS

Humulus japonicus reproduces by seed. Its small seeds are dispersed by mechanical means, most notably by wind and by the moving water of rivers and streams.


DISTRIBUTION

Humulus japonicus is native to eastern Asia. In North America its range is from southern Quebec and Ontario to northern Georgia and west from North Dakota to Kansas. It is found in all of the states of New England.


HISTORY OF INTRODUCTION IN NEW ENGLAND

It is unclear when Humulus japonicus was first brought to North America, but it probably arrived here for intentional cultivation. In New England, the earliest records of its escape and naturalization come from eastern Massachusetts and southern Connecticut at the end of the nineteenth century. There are also records from several locations in Vermont (Brattelboro, Burlington, Bellows Falls) from the early part of the twentieth century. Most of these early records note that Humulus japonicus had escaped to "waste places." Robinson (1908) described Humulus japonicus as having "occasionally escaped from frequent cultivation." By 1950, Fernald characterized it as being found in waste places, roadsides and along fencerows from New England to Michigan and south from Virginia and Missouri.


HABITATS IN NEW ENGLAND

Abandoned Field, Edge, Open Disturbed Area, River or Stream, Roadside, Vacant Lot, Yard or Garden
Humulus japonicus is often found in disturbed areas, along roadsides and utility right-of-ways, and in open fields, particularly when the soil is moist. It is also commonly found along river or stream banks and in floodplain areas, where it can form dense, almost continuous stands.


THREATS

When forming dense stands, Humulus japonicus can out compete native vegetation.


DOCUMENTATION NEEDS

Documentation required: A specific photograph or mounted snippet of the leaves with inflorescences.
Best time for documentation: Summer, fall.


REFERENCES

Bailey, L.H. 1949. Manual of Cultivated Plants. Macmillan, New
York.
Britton, N.L. and A. Brown. 1970. An Illustrated Flora of the
Northeastern United States vol. 1. Dover Publications Inc., New
York.
Fernald, M.L. 1950. Gray's Manual of Botany 8th ed. American Book
Co., Boston.
Flora of North America Editorial Committee, eds. 1993+. Flora of
North America North of Mexico. Volume #3. Oxford University
Press.
Flora of North America Association ed. 2000. Flora of North America
vol. 3. Oxford University Press, Oxford, New York.
Gleason H.A. and A.C. Cronquist. 1991. Manual of Vascular Plants
of the Northeastern United States and Adjacent Canada. 2nd ed.
New York Botanical Garden, Bronx, New York.
Holm, L.G., J.V. Pancho, J.P. Herberger, D.L. Plucknett. 1979. A
Geographical Atlas of World Weeds. John Wiley and Sons, New
York, USA.
Holmgren N.H. 1998. Illustrated Companion to Gleason and
Cronquist's Manual. New York Botanical Garden, Bronx, New York.
Magee D.W and H.E. Ahles. 1999. Flora of the Northeast. University
of Massachusetts Press, Amherst.
USDA, NRCS. 2001. The PLANTS Database, Version 3.1.
(http://plants.usda.gov). National Plant Data Center, Baton Rouge,
LA 70874-4490 USA.