Weed Information: Rhaponticum repens (knapweed, Russian)
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Rhaponticum repens (knapweed, Russian)

Family: Asteraceae

Description

The word `repens` in the scientific name means `creeping` and refers to the creeping root system of this rhizomatous perennial. The roots are usually black and scaly. The bracts beneath the flower heads are membranous and translucent. Note the EXTREMELY bitter taste of the leaves.

Characteristics

Flower Color
  • Red (or pink)
  • Purple
  • Red-purple
  • White
Inflorescence Type (How the flowers are arranged on the plant)
  • Corymb
  • Cyme (simple or branched)
  • Head
  • Panicle
Number of Petals
  • 0 (no petals)
  • 5 petals
  • more than 10 petals
Petal Separation
  • Completely free to base
  • United > 75% of length
Petal Tip
  • Pointed
Flower Symmetry
  • Flowers regular
Flower Length (Head length in the Asteraceae)
  • 8 mm (.32 inch)
  • 9 mm (.36 inch)
  • 1.0 cm (.40 inch)
  • 1.5 cm (.6 inch)
  • 2.0 cm (.8 inch)
Flower Width (Head width in the Asteraceae)
  • 8 mm (.32 inch)
  • 9 mm (.36 inch)
  • 1.0 cm (.40 inch)
  • 1.5 cm (.60 inch)
  • 2.0 cm (.80 inch)
Number of Sepals
  • sepals lacking
  • more than 10 sepals
Sepal Separation
  • Completely free to base
Sepal Tip
  • Pointed
Flower Sex
  • Bisexual (perfect)
Number of Styles
  • 1 style
Number of Stamens
  • 5 stamens
Stamens Attached to the Petals
  • Stamens attached to the petals
Stamens Connate (united)
  • Anthers united, syngynoecious

Carpel Separation
  • Carpels united (or one)
Number of Carpels
  • 1 carpel
Ovary Position
  • Inferior (epigynous)
Fruit Type
  • Achene
Fruit Length at Maturity
  • 2 mm (.08 inch)
  • 3 mm (.12 inch)
  • 4 mm (.16 inch)
Fruit Width at Maturity
  • 1 mm (.04 inch) or less
  • 2 mm (.08 inch)
Burs
  • Fruit or seed NOT bur-like

Leaf Arrangement
  • Alternate
Leaf Type
  • Simple (including lobed leaves)
Stipules
  • Lacking
Tendrils
  • Tendrils absent
Venation
  • Pinnate
Petiole (leaf stem) Blade Ratio
  • Petiole absent (leaf sessile)
  • Petiole < 25% total length
Leaf Length (blade PLUS petiole)
  • 1 - 2 cm (.40 - .80 inch)
  • 2 - 4 cm (.80 - 1.60 inches)
  • 4 - 10 cm (1.60 - 4.0 inches)
  • 1 - 2 dm (4.0 - 8.0 inches)
Leaf Width
  • 5 - 10 mm (.20 - .40 inch)
  • 1 - 2 cm (.40 - .80 inch)
  • 2 - 4 cm (.80 - 1.6 inches)
Leaf Shape (simple leaves only)
  • Lanceolate
  • Linear or filiform
  • Oblanceolate
  • Pinnately lobed
Leaf or Leaflet Margin
  • Entire
  • Lobed
Leaf or Leaflet Blade Base
  • Acuminate (attenuate)
  • Clasping
Leaf or Leaflet Tip
  • Acute
  • Rounded (obtuse)
Leaf or Leaflet Blade Surface
  • Glabrous (NO hairs)
  • Hispid or setose
  • Tomentose
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)
  • Erect, columnar (narrow)
  • 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)
Wind Dissemination
  • Fruit, seed, or spore wind borne
Moisture Regime
  • Seasonally saturated
  • Mesic
Chlorophyll
  • Present

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

Root or Vegetative Propagule
  • Rhizomatous

US State
  • Arkansas
  • Illinois
  • Kansas
  • Kentucky
  • Michigan
  • Missouri
  • Ohio
  • Texas
  • Wisconsin
  • Indiana
  • Arizona
  • California
  • Colorado
  • Iowa
  • Idaho
  • Minnesota
  • Montana
  • North Dakota
  • New Mexico
  • Nevada
  • Oklahoma
  • Oregon
  • South Dakota
  • Utah
  • Washington
  • Wyoming
  • Nebraska
Canadian Province or Territory
  • British Columbia
  • Ontario
  • Alberta
  • Manitoba
  • Saskatchewan

  • An Illustrated Guide To Arizona Weeds, 1972 (ISBN 0-8165-0288-9) 338 pages. See page: 284
  • The Biology of Canadian Weeds: Canadian Journal of Plant Science Vol:60Pg.993
  • California Growers Weed Identification Handbook, 1968 - 1998 University of California Publication # 4030-1, See page: 75
  • Common Weeds of the Canadian Prairies, 1963 (Cat# A53-1136-1) See page: 29
  • Common Weeds of the United States, 1971 (ISBN 0-486-20504-5) See page: 384
  • Field Guide To The Common Weeds Of Kansas, 1983 (ISBN 0-7006-0233-X) See page: 111
  • Fifty Important Weeds of Montana, Montana Ag. Ext. Service, 1920. 126 pages. See page: 54
  • Garden Weeds of Southern California, 1981, See page: 130
  • Gilkey`s Weeds of the Pacific Northwest, 1980 (ISBN 0-88246-039-0) See page: 335, 336
  • How to Know the Weeds, 1972, (ISBN# 0-697-04880-2) See page: 176
  • Nebraska Weeds, 1979 Nebraska Dept. of Ag., Lincoln NE, See page: 196
  • Northwest Weeds, 1990 (ISBN 0-87842-249-8) See page: 147
  • Ontario Weeds, 1992 Agdex 640, Publication #505 See page: 245
  • Selected Weeds of Oregon, 1985 and 1989 Supplement (s) Oregon State Dept. of Agriculture, See page: 77
  • South Dakota Weeds, 1967 South Dakota State University, See page: 19
  • South Dakota Weeds 2002 South Dakota Dept. of Ag. 523 E. Capitol, Foss Bldg. Pierre, South Dakota 57501 See page: 26/27
  • S.W.S.S. Weed ID Guide, 1993 Section Number and Five letter code: 13 CENRE
  • Weed Seeds of the Great Plains, 1993 University of Kansas# 92-125-B ISBN# 0-7006-0651-3 See index #: 205
  • Weeds, 1955 (1980) Walter Conrad Muenscher, ISBN# 0-8014-1266-8 See page: 444
  • Weeds, A Golden Guide, 1972 ISBN#0-307-24353-2 See page: 147
  • Weeds, 1957 Illinois State Dept. of Ag., See page: 18
  • Weeds and Poisonous Plants of Wyoming and Utah 1987 (ISBN 0-941570-06-1) See page: 166
  • Weeds of Alberta, 1983 Alberta Environmental Centre Agdex 640-4, See page: 195
  • Weeds of California, 1970, State of California Publications and Documents. See page: 442
  • Weeds of California and other Western States, 2007 (ISBN 13: 978-1-879906-69-3) See Page: 175
  • Weeds of Canada, 1970 Canada Dept. of Ag., Pub. # 948, See page: 191
  • Weeds of Colorado, 1990 Cooperative Extension, Colorado State Univ. Bulletin 521A, See page: 169
  • Weeds of Eastern Washington and Adjacent Areas, 1972 (LOC 72-83635) See page: 282
  • Weeds of Nebraska and the Great Plains, 1994 (ISBN 0939870-00-4) See page: 104
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  • Weeds of the North Central States, 1981 Univ. of Illinois, Urbana - Champaign Bulletin # 772, See page: 195
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  • Weeds of the West, 2000 (ISBN 0941570-13-4) See page: 44
  • Weeds of Utah, 1971 UAES Special Report 21, See page: 93
  • 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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