Weed Information: Onopordum acanthium (thistle, Scotch)
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Onopordum acanthium (thistle, Scotch)

Family: Asteraceae

Description

The scientific name comes from the Latin `onos` for donkey and refers to the supposed effect of causing flatulence in donkeys. (Make up your own common name!) An enormous biennial with rosettes to 6 feet wide and plants 6-12 feet tall. The leaves and stems are covered with white, cobwebby to felty hairs, and the stems have prominent, spiny wings. This species can grow in a great variety of soils and sites. The photos on page 225 of the California Growers Guide are actually bull thistle (Cirsium vulgare); however, the text on the back seems to be accurate for Scotch thistle.

Characteristics

Flower Color
  • Blue-purple
  • Purple
  • Red-purple
Inflorescence Type (How the flowers are arranged on the plant)
  • Corymb
  • Cyme (simple or branched)
  • Head
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)
  • 2.5 cm (1.0 inch)
  • 3.0 cm (1.2 inches)
  • 3.5 cm (1.4 inches)
  • 4.0 cm (1.6 inches)
  • 4.5 cm (1.8 inches)
  • 5.0 cm (2.0 inches) or more
Flower Width (Head width in the Asteraceae)
  • 3.5 cm (1.4 inches)
  • 4.0 cm (1.6 inches)
  • 4.5 cm (1.8 inches)
  • 5.0 cm (2.0 inches)
  • > 5.0 cm (> 2.0 inches)
Number of Sepals
  • sepals lacking
  • more than 10 sepals
Sepal Separation
  • Completely free to base
Sepal Tip
  • Spine-like
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
  • 4 mm (.16 inch)
  • 5 mm (.20 inch)
  • 6 mm (.24 inch)
Fruit Width at Maturity
  • 1 mm (.04 inch) or less
  • 2 mm (.08 inch)
  • 3 mm (.12 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 dm (4.0 - 8.0 inches)
  • 2 - 4 dm (8.0 - 16.0 inches)
  • 4 - 6 dm (1.3 - 2.0 feet)
  • > 6 dm (> 2.0 feet)
Leaf Width
  • 4 - 10 cm (1.6 - 4.0 inches)
  • 1 - 2 dm (4.0 - 8.0 inches)
  • 2 - 4 dm (8.0 - 16.0 inches)
  • > 4 dm (>1.3 feet)
Leaf Shape (simple leaves only)
  • Oblanceolate
  • Oblong
  • Obovate
  • Pinnately lobed
Leaf or Leaflet Margin
  • Lobed
Leaf or Leaflet Blade Base
  • Clasping
Leaf or Leaflet Tip
  • Aristate
Leaf or Leaflet Blade Surface
  • Floccose
  • Spiny or prickly
  • Tomentose
Succulence
  • Not succulent

Milky Juice
  • Juice NOT milky (watery)
Woodiness
  • Herbaceous
Spines or Thorns
  • Spines on leaves or stems
  • Spines on flowers\fruits AND leaves\stems
Aromatic (vegetative structures)
  • Not aromatic
Life Cycle
  • Biennial
Growth Habit (while flowering)
  • Erect, columnar (narrow)
Plant Height at Maturity
  • 6 - 8 dm (2.0 - 2.6 feet)
  • 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
  • Fruit, seed, or spore wind borne
Moisture Regime
  • Mesic
  • Arid
Chlorophyll
  • Present

Stem Cross Section
  • Hollow (flowering stem at maturity)
  • Round
  • Winged
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
  • Connecticut
  • Delaware
  • Florida
  • Illinois
  • Kansas
  • Kentucky
  • Massachusetts
  • Michigan
  • Missouri
  • New Jersey
  • New York
  • Ohio
  • Pennsylvania
  • Texas
  • Virginia
  • Wisconsin
  • West Virginia
  • Indiana
  • Maryland
  • Rhode Island
  • Vermont
  • Arizona
  • California
  • Colorado
  • Iowa
  • Idaho
  • Minnesota
  • Montana
  • New Mexico
  • Nevada
  • Oklahoma
  • Oregon
  • Utah
  • Washington
  • Wyoming
  • Nebraska
Canadian Province or Territory
  • British Columbia
  • New Brunswick
  • Nova Scotia
  • Ontario
  • Quebec
  • Manitoba
  • Newfoundland
Other
  • District of Columbia

  • California Growers Weed Identification Handbook, 1968 - 1998 University of California Publication # 4030-1, See page: 225
  • Field Guide To The Common Weeds Of Kansas, 1983 (ISBN 0-7006-0233-X) See page: 123
  • Gilkey`s Weeds of the Pacific Northwest, 1980 (ISBN 0-88246-039-0) See page: 347
  • Manual of Ohio Weeds, 1931 Ohio Ag. Exp. Station Bull. # 475, See page: 106
  • Nebraska Weeds, 1979 Nebraska Dept. of Ag., Lincoln NE, See page: 195
  • Northwest Weeds, 1990 (ISBN 0-87842-249-8) See page: 141
  • Ontario Weeds, 1992 Agdex 640, Publication #505 See page: 241
  • Selected Weeds of Oregon, 1985 and 1989 Supplement (s) Oregon State Dept. of Agriculture, See page: 89
  • South Dakota Weeds 2002 South Dakota Dept. of Ag. 523 E. Capitol, Foss Bldg. Pierre, South Dakota 57501 See page: 216
  • S.W.S.S. Weed ID Guide, 1993 Section Number and Five letter code: 13 ONRAC
  • Weed Seeds of the Great Plains, 1993 University of Kansas# 92-125-B ISBN# 0-7006-0651-3 See index #: 237
  • Weeds and Poisonous Plants of Wyoming and Utah 1987 (ISBN 0-941570-06-1) See page: 202
  • Weeds of California and other Western States, 2007 (ISBN 13: 978-1-879906-69-3) See Page: 372
  • Weeds of Colorado, 1990 Cooperative Extension, Colorado State Univ. Bulletin 521A, See page: 174
  • Weeds of Eastern Washington and Adjacent Areas, 1972 (LOC 72-83635) See page: 316
  • Weeds of Nebraska and the Great Plains, 1994 (ISBN 0939870-00-4) See page: 168
  • Weeds of the Midwestern United States & Central Canada, University of Georgia 2010, ISBN#0-8203-3506-1 See page: 114
  • Weeds of the North Central States, 1981 Univ. of Illinois, Urbana - Champaign Bulletin # 772, See page: 203
  • Weeds of the Northern United States and Canada, 1964 Montgomery See page: 189
  • Weeds of the West, 1992 (ISBN 0941570-13-4) See page: 164
  • Weeds of the West, 2000 (ISBN 0941570-13-4) See page: 164
  • Weeds of Utah, 1971 UAES Special Report 21, See page: 104
  • 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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