Grass-roots community organisation that aims to improve the natural condition of the Derwent catchment

Californian Thistle


The following page is a brief summary of information available on the DPIPWE website regarding Californian Thistle control. For more information view here

Non-chemical control

Physical removal

  • Mowing and slashing the above-ground parts of Californian Thistle are not effective as the root system is not removed and seed plays a relatively minor role in spread.


  • Cultivation alone will not control Californian Thistle. However, cultivation is important in an integrated control program, especially where large, well-established infestations are involved.
  • Cultivation is used to smash up the root system and force the root buds to germinate.
  • For the initial working, use a tool with deep penetrating blades such as a chisel plough and work to the depth to which the Thistle roots have penetrated.
  • Subsequent cultivations can be done with shallower working implements which sever the growing stems and drag the root fragments to the surface.
  • The first cultivation should be carried out in the spring before Thistle growth and while the ground is moist to allow deep working. Later cultivations should be carried out during the spring, summer and early autumn, to destroy the tops of the Thistles before they flower.
  • If used alone, between three and five cultivations may be needed in a season.
  • Cultivation can be followed by a forage crop (such as an autumn cereal) or pasture.
  • Californian Thistle seedlings are suppressed by crops which reduce the sunlight below 20% of full daylight.
  • Following cultivation, the area can be sown down to permanent pasture in the autumn and a herbicide follow-up program used. Care must be taken to ensure a strong and rapid pasture establishment.
  • In some crops such as Lucerne and berry fruits, Californian Thistle can be difficult to control. The weed should be eliminated before these crops are planted.


  • Grazing is not effective in controlling Californian Thistle. Sheep and goats will graze young shoots in spring but grazing alone will not eradicate or stop the spread of Californian Thistle.

Chemical control

Use herbicides in accordance with label. Refer to APVMA permit PER13160 where herbicide is to be used in non-cropping and bushland areas

Application method

1. Boom spraying

  • Stage of growth - Actively growing/Flowering
  • Location -  pasture and non-cropping
  • Suggested herbicide - Roundup®Biactive™

2. Spot spraying

  • Stage of growth (a) - From early bud to flowering
  • Location - pasture and non-cropping (non-clover/medic pasture)
  • Suggested herbicide - Lontrel®750 S
  • Stage of growth (b) - flowering
  • Location - pasture and non-cropping
  • Suggested herbicide - Roundup®Biactive™

Derwent Catchment Project

PO Box 22 Hamilton TAS 7140  |  Phone (03) 6286 3211  |