Weed Information: Polygonum argyrocoleon (knotweed, silversheath)
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Polygonum argyrocoleon (knotweed, silversheath)

Family: Polygonaceae

Description

An erect annual, the membranous stipules with long, free segments at the tip. In the 1991 edition of Weeds of the West, a photo of prostrate knotweed is misidentified as this species. When the photo was renamed in the 1992 through 2004 editions, the text was changed so that it now reads `prostrate annual, 1 to 3 feet tall.`

Characteristics

Flower Color
  • Red (or pink)
  • White
Inflorescence Type (How the flowers are arranged on the plant)
  • Axillary racemes
  • Axillary spikes
  • Terminal raceme
  • Terminal spike
Number of Petals
  • 0 (no petals)
  • 5 petals
Petal Separation
  • Completely free to base
  • United at base only (<25% length)
Petal Tip
  • Pointed
  • Rounded
Flower Symmetry
  • Flowers regular
Flower Length (Head length in the Asteraceae)
  • 1 mm (.04 inch)
  • 2 mm (.08 inch)
Flower Width (Head width in the Asteraceae)
  • 2 mm (.08 inch)
  • 3 mm (.12 inch)
  • 4 mm (.16 inch)
Number of Sepals
  • sepals lacking
  • 5 sepals
Sepal Separation
  • Completely free to base
  • United at base < 25% length
Sepal Tip
  • Pointed
  • Rounded
Flower Sex
  • Bisexual (perfect)
Number of Styles
  • 2 styles
  • 3 styles
Number of Stamens
  • 8 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
  • 2 carpels
  • 3 carpels
Ovary Position
  • Superior (hypogynous)
Fruit Type
  • Achene
Fruit Length at Maturity
  • 2 mm (.08 inch)
Fruit Width at Maturity
  • 1 mm (.04 inch) or less
Burs
  • Fruit or seed NOT bur-like

Leaf Arrangement
  • Alternate
Leaf Type
  • Simple (including lobed leaves)
Stipules
  • Membranous, laciniate
Tendrils
  • Tendrils absent
Venation
  • Pinnate
Petiole (leaf stem) Blade Ratio
  • Petiole < 25% total length
Leaf Length (blade PLUS petiole)
  • 1 - 2 cm (.40 - .80 inch)
  • 2 - 4 cm (.80 - 1.60 inches)
Leaf Width
  • 1 - 5 mm (.04 - .20 inch)
  • 5 - 10 mm (.20 - .40 inch)
Leaf Shape (simple leaves only)
  • Lanceolate
  • Linear or filiform
Leaf or Leaflet Margin
  • Entire
Leaf or Leaflet Blade Base
  • Acute (cuneate)
  • Acuminate (attenuate)
Leaf or Leaflet Tip
  • Acute
  • Rounded (obtuse)
Leaf or Leaflet Blade Surface
  • Glabrous (NO hairs)
Succulence
  • Not succulent

Milky Juice
  • Juice NOT milky (watery)
Woodiness
  • Herbaceous
Spines or Thorns
  • Spines or Thorns ABSENT
Aromatic (vegetative structures)
  • Not aromatic
Life Cycle
  • Annual
Growth Habit (while flowering)
  • Erect, spherical (bushy)
Plant Height at Maturity
  • 2 - 4 dm (8.0 - 16.0 inches)
  • 4 - 6 dm (1.3 - 2.0 feet)
  • 6 - 8 dm (2.0 - 2.6 feet)
  • 8 - 10 dm (2.6 - 3.3 feet)
Wind Dissemination
  • Not wind disseminated
Moisture Regime
  • Seasonally saturated
  • Mesic
Chlorophyll
  • Present

Stem Cross Section
  • Ridged
  • Round
Flowering Stem Leaves
  • Stem leaves greatly reduced
  • Stem uniformly leafy
Main Stem Branches
  • Main stem branched

Root or Vegetative Propagule
  • Tap Root

US State
  • Alabama
  • Florida
  • Massachusetts
  • Missouri
  • North Carolina
  • Texas
  • West Virginia
  • Hawaii
  • Vermont
  • Arizona
  • California
  • Colorado
  • Idaho
  • New Mexico
  • Nevada
  • Utah

  • An Illustrated Guide To Arizona Weeds, 1972 (ISBN 0-8165-0288-9) 338 pages. See page: 82
  • California Growers Weed Identification Handbook, 1968 - 1998 University of California Publication # 4030-1, See page: 80
  • Weeds, 1955 (1980) Walter Conrad Muenscher, ISBN# 0-8014-1266-8 See page: 164
  • Weeds of California, 1970, State of California Publications and Documents. See page: 131, 132
  • Weeds of California and other Western States, 2007 (ISBN 13: 978-1-879906-69-3) See Page: 1331
  • 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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