Nodding thistle (Carduus nutans)

Nodding thistle

(Carduus nutans)

Description

  • Solitary flowers at the end of a 20cm-2.5m tall stem
  • Alternate leaves, waxy cuticle
  • Flowers are purple-red with spiny bracts surrounding the flower.
  • Called ‘nodding thistle’ because the flowers droop down as they mature.

Consequences of invasion

  • A problem in grasslands where grazing animals favour grasses over the thistle, giving it an growth advantage
  • Outcompetes native grasses
  • Creates impenetrable thickets

Introduction and spread

  • Native to Europe
  • A nodding thistle plant may produce up to 20 000 seeds
  • Seeds can be transported to new areas via vehicles, equipment or clothing
  • Prefers to establish on disturbed sites.

Integrated Pest Management Options

Prevention

  • Learn to properly identify nodding thistle
  • Clean equipment and gear before leaving an infested site

Treatment

  • Hand digging and mowing can be effective if repeated over a period of time
  • Mow just before plants flower to reduce seed production.
  • Transport securely and dispose of removed invasive species properly at a landfill

Additional resources:

Nodding Thistle Photo Gallery | ISCBC

USDA National Invasive Species Information Centre

Nodding Thistle | Invasive Species Council of Manitoba