Weed Information: Acanthospermum australe (starbur, Paraguay)
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Acanthospermum australe (starbur, Paraguay)

Family: Asteraceae

Description

A prostrate to ascending annual often found in sandy soils. The fruit is a five to eight parted bur with hooked wings on the ridges. This species is common primarily in the Southeastern United States but, due to its means of dissemination, it can be expected to be found elsewhere (note the Oregon records).

Characteristics

Flower Color
  • Yellow
Inflorescence Type (How the flowers are arranged on the plant)
  • Axillary cluster
  • Head
  • Solitary, axillary
  • Solitary, terminal
Number of Petals
  • 0 (no petals)
  • 5 petals
Petal Separation
  • Completely free to base
  • United > 75% of length
Petal Tip
  • Pointed
  • Rounded
  • 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
  • 7 mm (.28 inch)
  • 8 mm (.32 inch)
  • 9 mm (.36 inch)
  • 1.0 cm (.40 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 < 25% total length
Leaf Length (blade PLUS petiole)
  • 1 - 2 cm (.40 - .80 inch)
  • 2 - 4 cm (.80 - 1.60 inches)
Leaf Width
  • 5 - 10 mm (.20 - .40 inch)
  • 1 - 2 cm (.40 - .80 inch)
  • 2 - 4 cm (.80 - 1.6 inches)
Leaf Shape (simple leaves only)
  • Deltoid (triangular)
  • Ovate
  • Rhombic (diamond)
Leaf or Leaflet Margin
  • Dentate
Leaf or Leaflet Blade Base
  • Acute (cuneate)
Leaf or Leaflet Tip
  • Acute
  • Rounded (obtuse)
Leaf or Leaflet Blade Surface
  • Glabrous (NO hairs)
  • Glandular
  • Scabrous (like sand paper)
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)
  • Prostrate
  • Spreading ascending
Plant Height at Maturity
  • 1 - 5 cm (.40 - 2.0 inches)
  • 5 - 10 cm (2.0 - 4.0 inches)
Wind Dissemination
  • Not wind disseminated
Moisture Regime
  • Seasonally saturated
  • Mesic
  • Arid
Chlorophyll
  • Present

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

Root or Vegetative Propagule
  • Fibrous

US State
  • Alabama
  • Arkansas
  • Florida
  • Georgia
  • Louisiana
  • Massachusetts
  • Mississippi
  • North Carolina
  • New York
  • Pennsylvania
  • South Carolina
  • Tennessee
  • Texas
  • Virginia
  • Hawaii
  • Oregon

  • Listed as a `Weed` by the Biota of North America Program, 2008 X
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