Weed Information: Rudbeckia hirta (blackeyed-Susan)
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Rudbeckia hirta (blackeyed-Susan)

Family: Asteraceae

Description

A native wildflower occurring throughout much of the United States. The common name derived from the dark colored disk flowers. Often found on roadsides and disturbed sites, where certainly preferable to many other species! Rudbeckia hirta var. pulcherimma This native biennial to perennial can flower the first year (most perennials do not). This trait is consistent with the fact that this variety found in the Great Plains is rather weedy and often found in disturbed sites. The ray flowers are yellow, often purplish near the base, and the center elongates at maturity, forming the `cone` referred to in the common name. Although listed by WSSA, the typical variety (Rudbeckia hirta) is an eastern wildflower which does not occur in disturbed sites (is NOT a weed).

Characteristics

Flower Color
  • Orange
  • Yellow-orange
  • Yellow
  • Purple
  • Red-purple
  • Brown/Black
  • Multi-colored
Inflorescence Type (How the flowers are arranged on the plant)
  • Head
  • Solitary, terminal
Number of Petals
  • 5 petals
  • 8 petals
  • 9 petals
  • 10 petals
  • more than 10 petals
Petal Separation
  • Completely free to base
  • United > 75% of length
Petal Tip
  • Bilobed
  • Rounded
Flower Symmetry
  • Flowers regular
Flower Length (Head length in the Asteraceae)
  • 1.0 cm (.40 inch)
  • 1.5 cm (.6 inch)
  • 2.0 cm (.8 inch)
  • 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)
  • 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
  • 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
  • Arcuate
  • Palmate
  • Pinnate
Petiole (leaf stem) Blade Ratio
  • Petiole absent (leaf sessile)
  • Petiole < 25% total length
Leaf Length (blade PLUS petiole)
  • 4 - 10 cm (1.60 - 4.0 inches)
  • 1 - 2 dm (4.0 - 8.0 inches)
Leaf Width
  • 1 - 2 cm (.40 - .80 inch)
  • 2 - 4 cm (.80 - 1.6 inches)
  • 4 - 10 cm (1.6 - 4.0 inches)
Leaf Shape (simple leaves only)
  • Elliptic
  • Lanceolate
  • Linear or filiform
  • Oblanceolate
  • Oblong
  • Oval
  • Ovate
  • Spatulate
Leaf or Leaflet Margin
  • Crenate
  • Dentate
  • Entire
  • Serrate
Leaf or Leaflet Blade Base
  • Acuminate (attenuate)
  • Rounded
Leaf or Leaflet Tip
  • Acuminate (attenuate)
  • Acute
Leaf or Leaflet Blade Surface
  • Canescent
  • Hirsute
  • Hispid or setose
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
  • Biennial
  • Perennial
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)
Wind Dissemination
  • Not wind disseminated
Moisture Regime
  • Mesic
Chlorophyll
  • Present

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

Root or Vegetative Propagule
  • Fibrous
  • 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
  • Indiana
  • Maryland
  • Rhode Island
  • Vermont
  • Alaska
  • California
  • Colorado
  • Iowa
  • Idaho
  • Minnesota
  • Montana
  • North Dakota
  • New Mexico
  • 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
Other
  • District of Columbia

  • Common Weeds of Canada, Mulligan 1987 (ISBN 0-910053-59-9) See page: 127
  • Garden Weeds of Southern California, 1981, See page: 128
  • How to Know the Weeds, 1972, (ISBN# 0-697-04880-2) See page: 184
  • Manual of Ohio Weeds, 1931 Ohio Ag. Exp. Station Bull. # 475, See page: 92
  • More Turfgrass and Related Weeds: Beyond the Color Atlas, 2011 Clemson University Publishing ISBN# 978-0-9798777-5-9 See Page: 189
  • Ontario Weeds, 1992 Agdex 640, Publication #505 See page: 209
  • Representative Missouri Weeds and Their Control, 1941 Univ. of Missouri Ag. Exp Station Bulletin #433, See page: 203
  • South Dakota Weeds, 1967 South Dakota State University, See page: 184
  • Weeds, 1955 (1980) Walter Conrad Muenscher, ISBN# 0-8014-1266-8 See page: 491
  • Weeds, A Golden Guide, 1972 ISBN#0-307-24353-2 See page: 133
  • Weeds of Arkansas 1981 (MP 169-5M-3-81) See page: 18
  • Weeds of California, 1970, State of California Publications and Documents. See page: 490, 491
  • Weeds of the Midwestern United States & Central Canada, University of Georgia 2010, ISBN#0-8203-3506-1 See page: 116
  • Weeds of the North Central States, 1981 Univ. of Illinois, Urbana - Champaign Bulletin # 772, See page: 228
  • Weeds of the Northeast, 1956, Univ. of Delaware Field Manual #1 See species #: 109
  • Weeds of the Northern United States and Canada, 1964 Montgomery See page: 189
  • Weeds of the South, University of Georgia 2009, ISBN#0-8203-3046-9 See page: 98
  • Weeds of the United States and Their Control, Lorenzi 1987, ISBN# 0-442-25884-4 See page: 322
  • Wildly Successful Plants, A Handbook of North American Weeds, 1977 (ISBN# 0-02-528850-4) See page: 25, 169
  • 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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