Weed Information: Humulus japonicus (hops, Japanese)
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Humulus japonicus (hops, Japanese)

Family: Cannabaceae

Description

Herbaceous vines with opposite leaves. The male flowers in panicles; the female flowers in dense, bracteate spikes.

Characteristics

Flower Color
  • Yellow-green
  • Green
Inflorescence Type (How the flowers are arranged on the plant)
  • Axillary spikes
  • Panicle
Number of Petals
  • 0 (no petals)
Flower Symmetry
  • Flowers regular
Flower Length (Head length in the Asteraceae)
  • < 1 mm (< .04 inch)
  • 1 mm (.04 inch)
Flower Width (Head width in the Asteraceae)
  • < 1 mm (< .04 inch)
  • 1 mm (.04 inch)
Number of Sepals
  • 5 sepals
Sepal Separation
  • Completely free to base
Sepal Tip
  • Pointed
Flower Sex
  • Unisexual (monoecious or dioecious)
Number of Styles
  • Styles lacking (male flowers only)
  • 1 style
Number of Stamens
  • stamens lacking (female flowers only)
  • 5 stamens
Stamens Attached to the Petals
  • Stamens NOT attached to the petals
Stamens Connate (united)
  • Filaments or anthers NOT united

Carpel Separation
  • Carpels united (or one)
Number of Carpels
  • 0 (male flowers only or plants producing spores)
  • 1 carpel
  • 2 carpels
Ovary Position
  • Superior (hypogynous)
Fruit Type
  • Achene
Fruit Length at Maturity
  • 4 mm (.16 inch)
  • 5 mm (.20 inch)
Fruit Width at Maturity
  • 4 mm (.16 inch)
  • 5 mm (.20 inch)
Burs
  • Fruit or seed NOT bur-like

Leaf Arrangement
  • Opposite
Leaf Type
  • Simple (including lobed leaves)
Stipules
  • Foliaceous 2-4 mm (.08 - .16 in) long
  • Foliaceous 4-10 mm (.16 - .40 in) long
Tendrils
  • Tendrils absent
Venation
  • Palmate
Petiole (leaf stem) Blade Ratio
  • Petiole 25% - 75% total length
  • Petiole > 75% total length
Leaf Length (blade PLUS petiole)
  • 1 - 2 dm (4.0 - 8.0 inches)
  • 2 - 4 dm (8.0 - 16.0 inches)
Leaf Width
  • 4 - 10 cm (1.6 - 4.0 inches)
  • 1 - 2 dm (4.0 - 8.0 inches)
Leaf Shape (simple leaves only)
  • Ovate
  • Palmately 4 - 5 lobed
  • Palmately > 5 lobed
Leaf or Leaflet Margin
  • Serrate
  • Serrate, doubly
Leaf or Leaflet Blade Base
  • Cordate
Leaf or Leaflet Tip
  • Acuminate (attenuate)
  • Acute
Leaf or Leaflet Blade Surface
  • Hirsute
  • Lower leaf surface more hairy
  • Pubescent
  • Scabrous (like sand paper)
  • Spiny or prickly
Succulence
  • Not succulent

Milky Juice
  • Juice NOT milky (watery)
Woodiness
  • Herbaceous
Spines or Thorns
  • Spines or Thorns ABSENT
Aromatic (vegetative structures)
  • Not aromatic
  • Aromatic
Life Cycle
  • Perennial
Growth Habit (while flowering)
  • Climbing vine
Plant Height at Maturity
  • 8 - 10 dm (2.6 - 3.3 feet)
  • 1 - 1.5 meters (3.3 - 5.0 feet)
  • 1.5 - 2.0 meters (5.0 - 6.6 feet)
  • 2 - 2.5 meters (6.6 - 8.3 feet)
  • 2.5 - 5 meters (8.3 - 16.6 feet)
Wind Dissemination
  • Not wind disseminated
Moisture Regime
  • Seasonally saturated
  • Mesic
Chlorophyll
  • Present

Stem Cross Section
  • Ridged
  • Square
Flowering Stem Leaves
  • Stem uniformly leafy
Main Stem Branches
  • Main stem branched

Root or Vegetative Propagule
  • Fibrous
  • Tap Root

US State
  • Alabama
  • Arkansas
  • Connecticut
  • Delaware
  • Georgia
  • Illinois
  • Kansas
  • Kentucky
  • Massachusetts
  • Maine
  • Michigan
  • Missouri
  • North Carolina
  • New Hampshire
  • New Jersey
  • New York
  • Ohio
  • Pennsylvania
  • South Carolina
  • Tennessee
  • Virginia
  • Wisconsin
  • West Virginia
  • Indiana
  • Maryland
  • Rhode Island
  • Vermont
  • Iowa
  • Minnesota
  • North Dakota
  • South Dakota
  • Nebraska
Other
  • District of Columbia
Canadian Province or Territory
  • Ontario
  • Quebec

  • Pennsylvania Field Guide, Common Invasive Plants in Riparian Areas, 2004 See Page: 17
  • Listed as a `Weed` by the Biota of North America Program, 2008 x
  • Listed in the WSSA Composite List of Weeds X
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