Weed Information: Sonchus oleraceus (sowthistle, annual)
Back to Plant List

Sonchus oleraceus (sowthistle, annual)

Family: Asteraceae

Description

The common name is somewhat deceptive since this is not our only sowthistle which is annual. It is most often confused with spiny sowthistle (Sonchus asper) which is mush more spiny. Spiny sowthistle has rounded auricles (ears) at the leaf bases, while those of annual sowthistle are pointed. Seedlings and young plants of this species often have watery juice, but mature plants have milky juice.

Characteristics

Flower Color
  • Yellow
Inflorescence Type (How the flowers are arranged on the plant)
  • Cyme (simple or branched)
  • Head
  • Panicle
Number of Petals
  • 5 petals
  • more than 10 petals
Petal Separation
  • Completely free to base
  • United > 75% of length
Petal Tip
  • Square
  • Toothed
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)
Flower Width (Head width in the Asteraceae)
  • 1.5 cm (.60 inch)
  • 2.0 cm (.80 inch)
  • 2.5 cm (1.0 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
  • Petiole 25% - 75% total length
Leaf Length (blade PLUS petiole)
  • 4 - 10 cm (1.60 - 4.0 inches)
  • 1 - 2 dm (4.0 - 8.0 inches)
  • 2 - 4 dm (8.0 - 16.0 inches)
Leaf Width
  • 1 - 2 cm (.40 - .80 inch)
  • 2 - 4 cm (.80 - 1.6 inches)
  • 4 - 10 cm (1.6 - 4.0 inches)
  • 1 - 2 dm (4.0 - 8.0 inches)
Leaf Shape (simple leaves only)
  • Oblanceolate
  • Obovate
  • Ovate
  • Pinnately lobed
  • Runcinate
Leaf or Leaflet Margin
  • Dentate
  • Lobed
  • Parted
  • Serrate
Leaf or Leaflet Blade Base
  • Acuminate (attenuate)
  • Auriculate
  • Clasping
  • Perfoliate
Leaf or Leaflet Tip
  • Acuminate (attenuate)
  • Acute
  • Rounded (obtuse)
Leaf or Leaflet Blade Surface
  • Glabrous (NO hairs)
  • Spiny or prickly
Succulence
  • Not succulent

Milky Juice
  • Juice NOT milky (watery)
  • Juice milky
Woodiness
  • Herbaceous
Spines or Thorns
  • Spines or Thorns ABSENT
Aromatic (vegetative structures)
  • Not aromatic
Life Cycle
  • Annual
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)
  • 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)
Wind Dissemination
  • Fruit, seed, or spore wind borne
Moisture Regime
  • Mesic
Chlorophyll
  • Present

Stem Cross Section
  • Hollow (flowering stem at maturity)
  • Round
Flowering Stem Leaves
  • Stem uniformly leafy
Main Stem Branches
  • Main stem branched

Root or Vegetative Propagule
  • Tap Root

US State
  • Alabama
  • Arkansas
  • Connecticut
  • Delaware
  • Florida
  • Georgia
  • Illinois
  • Kansas
  • Kentucky
  • Louisiana
  • Massachusetts
  • Maine
  • Michigan
  • Missouri
  • Mississippi
  • North Carolina
  • New Hampshire
  • New Jersey
  • New York
  • Ohio
  • Pennsylvania
  • South Carolina
  • Tennessee
  • Texas
  • Virginia
  • Wisconsin
  • West Virginia
  • Hawaii
  • Indiana
  • Maryland
  • Rhode Island
  • Vermont
  • Alaska
  • 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
  • New Brunswick
  • Nova Scotia
  • Ontario
  • Prince Edward Island
  • Quebec
  • Alberta
  • Manitoba
  • Newfoundland
  • Saskatchewan
  • Yukon
  • Northwest Territory
Other
  • Puerto Rico
  • Virgin Islands
  • District of Columbia
  • St. Pierre and Miquelon
  • Greenland

  • An Illustrated Guide To Arizona Weeds, 1972 (ISBN 0-8165-0288-9) 338 pages. See page: 318
  • The Biology of Canadian Weeds: Canadian Journal of Plant Science Vol:64Pg.731
  • California Growers Weed Identification Handbook, 1968 - 1998 University of California Publication # 4030-1, See page: 4
  • Common Weeds of Canada, Mulligan 1987 (ISBN 0-910053-59-9) See page: 132
  • Common Weeds of the Canadian Prairies, 1963 (Cat# A53-1136-1) See page: 62
  • Common Weeds of the United States, 1971 (ISBN 0-486-20504-5) See page: 436
  • Common Weed Seedlings of the United States and Canada, 1978 Coop Ext. Univ. of Georgia, Athens, See page: 14
  • Fifty Important Weeds of Montana, Montana Ag. Ext. Service, 1920. 126 pages. See page: 93
  • Garden Weeds of Southern California, 1981, See page: 116
  • Gilkey`s Weeds of the Pacific Northwest, 1980 (ISBN 0-88246-039-0) See page: 295, 296
  • How to Know the Weeds, 1972, (ISBN# 0-697-04880-2) See page: 161
  • Identification Guide to the Weeds of Quebec, 1999 (ISBN# 2-89457-174-7) See page: 56
  • Manual of Ohio Weeds, 1931 Ohio Ag. Exp. Station Bull. # 475, See page: 110
  • Northwest Weeds, 1990 (ISBN 0-87842-249-8) See page: 159
  • Ontario Weeds, 1992 Agdex 640, Publication #505 See page: 249
  • Weeds, 1955 (1980) Walter Conrad Muenscher, ISBN# 0-8014-1266-8 See page: 499, 500
  • Weeds, A Golden Guide, 1972 ISBN#0-307-24353-2 See page: 155
  • Weeds of California, 1970, State of California Publications and Documents. See page: 500
  • Weeds of California and other Western States, 2007 (ISBN 13: 978-1-879906-69-3) See Page: 398
  • Weeds of Canada, 1970 Canada Dept. of Ag., Pub. # 948, See page: 203
  • Weeds of Colorado, 1990 Cooperative Extension, Colorado State Univ. Bulletin 521A, See page: 184
  • Weeds of Eastern Washington and Adjacent Areas, 1972 (LOC 72-83635) See page: 326
  • Weeds of Nebraska and the Great Plains, 1994 (ISBN 0939870-00-4) See page: 175
  • Weeds of Nova Scotia, 1986 (ISBN# 0-88871-063) See page: 78
  • Weeds of Southern Turfgrasses, 1992 Univ. of Florida, Gainesville Publication # SP-79, See page: 109
  • Weeds of the Midwestern United States & Central Canada, University of Georgia 2010, ISBN#0-8203-3506-1 See page: 125
  • Weeds of the North Central States, 1981 Univ. of Illinois, Urbana - Champaign Bulletin # 772, See page: 235
  • Weeds of the Northeast, 1956, Univ. of Delaware Field Manual #1 See species #: 278
  • Weeds of the Northeast, 1997 Cornell University ISBN# 0-8014-8334-4 See page: 160, 366
  • Weeds of the Northern United States and Canada, 1964 Montgomery See page: 201
  • Weeds of the Northern U.S, and Canada, 1999 Royer and Dickinson, (ISBN# 1-55105-221-0) See page: 57
  • Weeds of the South, University of Georgia 2009, ISBN#0-8203-3046-9 See page: 106
  • Weeds of the United States and Their Control, Lorenzi 1987, ISBN# 0-442-25884-4 See page: 327
  • Weeds of the West, 1992 (ISBN 0941570-13-4) See page: 182
  • Weeds of the West, 2000 (ISBN 0941570-13-4) See page: 182
  • Weeds of Utah, 1971 UAES Special Report 21, See page: 106
  • Listed as a `Weed` by the Biota of North America Program, 2008 x
  • Listed in the WSSA Composite List of Weeds X
Back to Plant List