Cirsium arvense

Californian thistle

Family: Asteraceae

Origin: Eurasia

Three Californian thistle flower heads in bloom.
The red/pink/purple flower heads occur in the summer.

Regional Pest Management Plan (RPMP) status

  • Whole region — Sustained control
  • Hauraki Gulf Controlled Area Notice pest

View more about the RPMP statuses

General description

Rhizomatous perennial herb. Leaves are sessile, < 15 x 5 cm and oblong, with prickles < 1 cm long. Flowers are red/pink/purple and borne in December – February. Achenes have white pappus attached.

What you need to know

To help protect our environment, from 1 September 2021, you:

  • will not be allowed to breed, distribute, release or sell Californian thistle within the Auckland region.
  • will not be allowed to plant Californian thistle within the Auckland region, unless you are transferring an existing plant on your land to another location within the boundaries of the same property.
  • must destroy any Californian thistle on land that you occupy if it has been planted in breach of the above rules and you are directed to do so by an authorised person.


Pasture, roadsides, riparian margins, open coastal areas.


Seeds dispersed by wind. Vegetative spread from rhizomes. Human-mediated dispersal through contamination of machinery.

Impact on environment

Infests pasture, reducing milk and animal yields due to herbivore avoidance. Spines injure livestock’s mouths, promoting ‘scabby mouth disease’. Seed heads contaminate wool.


Site management

Maintaining good pasture cover can prevent establishment or suppress an infestation. Mowing before flowering will reduce spread of seeds.

Recommended approaches

Physical control

Method: Dig or grub out.

Plant parts requiring disposal: Seeds.

Disposal options: Remove to greenwaste or landfill if practical.


Check for presence of agents:

  • Californian thistle gall fly ( Urophora cardui).
  • Californian thistle leaf beetle (Lema cyanella).
  • Green thistle beetle (Cassida rubignosa).

For more information about how biocontrol works, see What is biocontrol?

Community agrichemical control recommendations

Basic Growsafe certified: Foliar spray with 100ml glyphosate green per 10L of water.

Safety notes

Plant has spines.

Caution: When using any herbicide or pesticide please read the label thoroughly to ensure that all instructions and safety requirements are followed.

Californian thistle with buds next to a stream.
The tendency to grow in patches is a distinguishing feature.
Thick patch of Californian thistles covering the ground.
Californian thistle has a spreading root system.
Close up shot of the Californian thistle flower heads in bloom.
The flower heads are smaller than many other thistle species.