Weed Information: Acanthospermum hispidum (starbur, bristly)
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Acanthospermum hispidum (starbur, bristly)

Family: Asteraceae

Description

The body of the fruit (seed) covered with spines as well as having two longer hooked spines at the apex. The leaves are opposite and the small flower heads arise singly from the leaf or branch axils. Each head has 5-10 fertile ray flowers and several sterile ray flowers.

Characteristics

Flower Color
  • Yellow
  • White
  • Multi-colored
Inflorescence Type (How the flowers are arranged on the plant)
  • Axillary cluster
  • Head
  • Solitary, axillary
  • Solitary, terminal
Number of Petals
  • 5 petals
  • 6 petals
  • 7 petals
  • 8 petals
  • 9 petals
  • 10 petals
Petal Separation
  • Completely free to base
  • United > 75% of length
Petal Tip
  • Pointed
  • Square
  • Toothed
Flower Symmetry
  • Flowers regular
Flower Length (Head length in the Asteraceae)
  • 3 mm (.12 inch)
  • 4 mm (.16 inch)
  • 5 mm (.20 inch)
Flower Width (Head width in the Asteraceae)
  • 3 mm (.12 inch)
  • 4 mm (.16 inch)
  • 5 mm (.20 inch)
Number of Sepals
  • sepals lacking
  • 4 sepals
  • 5 sepals
  • 6 sepals
Sepal Separation
  • Completely free to base
Sepal Tip
  • Pointed
  • Rounded
Flower Sex
  • Unisexual (monoecious or dioecious)
Number of Styles
  • Styles lacking (male flowers only)
  • 1 style
Number of Stamens
  • stamens lacking (female flowers only)
  • 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
  • 0 (male flowers only or plants producing spores)
  • 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)
  • 7 mm (.28 inch)
Fruit Width at Maturity
  • 3 mm (.12 inch)
  • 4 mm (.16 inch)
  • 5 mm (.20 inch)
  • 6 mm (.24 inch)
  • 7 mm (.28 inch)
  • 8 mm (.32 inch)
Burs
  • Fruit or seed bur-like

Leaf Arrangement
  • Opposite
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)
  • 2 - 4 cm (.80 - 1.60 inches)
  • 4 - 10 cm (1.60 - 4.0 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
  • Oval
  • Ovate
Leaf or Leaflet Margin
  • Dentate
Leaf or Leaflet Blade Base
  • Acute (cuneate)
  • Acuminate (attenuate)
Leaf or Leaflet Tip
  • Acute
  • Rounded (obtuse)
Leaf or Leaflet Blade Surface
  • Glandular
  • Puberulent
  • Pubescent
Succulence
  • Not succulent

Milky Juice
  • Juice NOT milky (watery)
Woodiness
  • Herbaceous
Spines or Thorns
  • Spines or Thorns ABSENT
  • Spines on flowers or fruits only
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)
Wind Dissemination
  • Not wind disseminated
Moisture Regime
  • Mesic
Chlorophyll
  • Present

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

Root or Vegetative Propagule
  • Tap Root

US State
  • Alabama
  • Florida
  • Georgia
  • New Jersey
  • South Carolina
  • Virginia
  • Hawaii
  • Oregon
Other
  • Puerto Rico
  • Virgin Islands
Canadian Province or Territory
  • Ontario

  • Common Weed Seedlings of the United States and Canada, 1978 Coop Ext. Univ. of Georgia, Athens, See page: 10
  • More Turfgrass and Related Weeds: Beyond the Color Atlas, 2011 Clemson University Publishing ISBN# 978-0-9798777-5-9 See Page: 154
  • S.W.S.S. Weed ID Guide, 1993 Section Number and Five letter code: 13 ACNHI
  • Weeds of the South, University of Georgia 2009, ISBN#0-8203-3046-9 See page: 47
  • Weeds of the Southern United States, 1975, North Carolina Ag. Extension Circular #599 See page: 8
  • Weeds of the United States and Their Control, Lorenzi 1987, ISBN# 0-442-25884-4 See page: 289
  • 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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