Weed Information: Erigeron canadensis (horseweed)
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Erigeron canadensis (horseweed)

Family: Asteraceae

Description

Also called mare`s tail, this species does not develop its small, white flower heads until mid to late summer. The leaves can be either entire or lobed. At all stages of growth, the leaves have stiff `ciliate` hairs along the margins. A very common weed along roadsides, this species has developed resistance to certain herbicides.

Characteristics

Flower Color
  • Yellow
  • White
  • Multi-colored
Inflorescence Type (How the flowers are arranged on the plant)
  • 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)
  • 2 mm (.08 inch)
  • 3 mm (.12 inch)
  • 4 mm (.16 inch)
  • 5 mm (.20 inch)
Flower Width (Head width in the Asteraceae)
  • 2 mm (.08 inch)
  • 3 mm (.12 inch)
  • 4 mm (.16 inch)
  • 5 mm (.20 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
  • 1 mm (.04 inch) or less
  • 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
  • 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)
Leaf Width
  • 1 - 5 mm (.04 - .20 inch)
  • 5 - 10 mm (.20 - .40 inch)
Leaf Shape (simple leaves only)
  • Linear or filiform
  • Oblanceolate
Leaf or Leaflet Margin
  • Dentate
  • Entire
  • Ciliate
Leaf or Leaflet Blade Base
  • Acuminate (attenuate)
Leaf or Leaflet Tip
  • Acute
Leaf or Leaflet Blade Surface
  • Glabrous (NO hairs)
  • Hispid or setose
  • Pubescent
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
  • Annual
Growth Habit (while flowering)
  • Erect, columnar (narrow)
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)
Wind Dissemination
  • Fruit, seed, or spore wind borne
Moisture Regime
  • 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
  • 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
  • Northwest Territory
Other
  • Puerto Rico
  • Virgin Islands
  • District of Columbia
  • St. Pierre and Miquelon

  • An Illustrated Guide To Arizona Weeds, 1972 (ISBN 0-8165-0288-9) 338 pages. See page: 290
  • The Biology of Canadian Weeds: Canadian Journal of Plant Science Vol:81Pg.867
  • California Growers Weed Identification Handbook, 1968 - 1998 University of California Publication # 4030-1, See page: 16
  • Common Weeds of Canada, Mulligan 1987 (ISBN 0-910053-59-9) See page: 112
  • Common Weeds of the Canadian Prairies, 1963 (Cat# A53-1136-1) See page: 36
  • Common Weeds of the United States, 1971 (ISBN 0-486-20504-5) See page: 400
  • Common Weed Seedlings of the North Central States, 2001 North Central Regional Extension Publication # 607 See page: 19
  • Common Weed Seedlings of the United States and Canada, 1978 Coop Ext. Univ. of Georgia, Athens, See page: 11
  • Field Guide To The Common Weeds Of Kansas, 1983 (ISBN 0-7006-0233-X) See page: 115
  • Garden Weeds of Southern California, 1981, See page: 108
  • Gilkey`s Weeds of the Pacific Northwest, 1980 (ISBN 0-88246-039-0) See page: 325
  • How to Know the Weeds, 1972, (ISBN# 0-697-04880-2) See page: 186
  • Identification Guide to the Weeds of Quebec, 1999 (ISBN# 2-89457-174-7) See page: 84
  • Manual of Ohio Weeds, 1931 Ohio Ag. Exp. Station Bull. # 475, See page: 100
  • Nebraska Weeds, 1979 Nebraska Dept. of Ag., Lincoln NE, See page: 206
  • Northwest Weeds, 1990 (ISBN 0-87842-249-8) See page: 129
  • Ontario Weeds, 1992 Agdex 640, Publication #505 See page: 230
  • Representative Missouri Weeds and Their Control, 1941 Univ. of Missouri Ag. Exp Station Bulletin #433, See page: 193
  • Some Important Michigan Weeds, 1951 Mich. Ag. Exp. Station Bulletin #304, See page: 219
  • South Dakota Weeds, 1967 South Dakota State University, See page: 181
  • South Dakota Weeds 2002 South Dakota Dept. of Ag. 523 E. Capitol, Foss Bldg. Pierre, South Dakota 57501 See page: 163
  • S.W.S.S. Weed ID Guide, 1993 Section Number and Five letter code: 13 ERICA
  • Weed Seeds of the Great Plains, 1993 University of Kansas# 92-125-B ISBN# 0-7006-0651-3 See index #: 213
  • Weeds, 1955 (1980) Walter Conrad Muenscher, ISBN# 0-8014-1266-8 See page: 459
  • Weeds, A Golden Guide, 1972 ISBN#0-307-24353-2 See page: 126
  • Weeds and Poisonous Plants of Wyoming and Utah 1987 (ISBN 0-941570-06-1) See page: 186
  • Weeds of Arkansas 1981 (MP 169-5M-3-81) See page: 14
  • Weeds of California, 1970, State of California Publications and Documents. See page: 462, 463
  • Weeds of California and other Western States, 2007 (ISBN 13: 978-1-879906-69-3) See Page: 284
  • Weeds of Canada, 1970 Canada Dept. of Ag., Pub. # 948, See page: 157
  • Weeds of Colorado, 1990 Cooperative Extension, Colorado State Univ. Bulletin 521A, See page: 149
  • Weeds of Eastern Washington and Adjacent Areas, 1972 (LOC 72-83635) See page: 296
  • Weeds of Kentucky and Adjacent States, 1991 (ISBN 0-8131-1743-7) See page: 16
  • Weeds of Nebraska and the Great Plains, 1994 (ISBN 0939870-00-4) See page: 122
  • Weeds of Southern Turfgrasses, 1992 Univ. of Florida, Gainesville Publication # SP-79, See page: 89
  • Weeds of the Midwestern United States & Central Canada, University of Georgia 2010, ISBN#0-8203-3506-1 See page: 83
  • Weeds of the North Central States, 1981 Univ. of Illinois, Urbana - Champaign Bulletin # 772, See page: 204
  • Weeds of the Northeast, 1956, Univ. of Delaware Field Manual #1 See species #: 134
  • Weeds of the Northeast, 1997 Cornell University ISBN# 0-8014-8334-4 See page: 236,140
  • Weeds of the Northern United States and Canada, 1964 Montgomery See page: 181
  • Weeds of the Northern U.S, and Canada, 1999 Royer and Dickinson, (ISBN# 1-55105-221-0) See page: 36
  • Weeds of the South, University of Georgia 2009, ISBN#0-8203-3046-9 See page: 69
  • Weeds of the Southern United States, 1975, North Carolina Ag. Extension Circular #599 See page: 11
  • Weeds of the United States and Their Control, Lorenzi 1987, ISBN# 0-442-25884-4 See page: 312
  • Weeds of the West, 1992 (ISBN 0941570-13-4) See page: 122
  • Weeds of the West, 2000 (ISBN 0941570-13-4) See page: 124
  • Weeds of Utah, 1971 UAES Special Report 21, See page: 97
  • 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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