Weed Seed: Hispid starbur (Acanthospermum hispidum)



Distribution in Canada

Present in ON

Duration of life cycle


Seed/Fruit type

Achene - a one-seeded, dry fruit

Seed identification features


  • length: 4.0–6.0 mm
  • width: 2.5–3.5 mm
  • thickness: 1.0–1.5 mm
  • spine length: 3.0– 4.0 mm


  • in outline: triangular
  • in cross section: rectangular

Surface texture

  • smooth and glossy
  • covered in 1.0 mm-long hooked spines


  • light brown to medium brown
  • spines tend to be darker

Other structures

  • two long, spreading spines (may be slightly curved) at top, or apex, of seed

Similar species

Low starbur (Acanthospermum humile)

  • found in southeastern United States and New York state
  • similar to hisbid starbur in triangular shape, medium-brown colour, and the presence of 2 long spines coming from apex
  • shorter and narrower than hisbid starbur by 0.5–1.0 mm
  • hooked spines run along only one side of achene (hooked spines cover the hispid starbur achene)
  • slightly curved to one side (hispid starbur achene is straight)


Photo - Hispid starbur (Acanthospermum hispidum) achene
Hispid starbur (Acanthospermum hispidum) achene
Photo - Hispid starbur (Acanthospermum hispidum) achenes
Hispid starbur (Acanthospermum hispidum) achenes

Similar species

Photo - Similar species: Low starbur (Acanthospermum humile) achenes
Similar species: Low starbur (Acanthospermum humile) achenes
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