What does it look like?
Variegated thistle is a biennial thistle. It can grow up to 2.5m tall and more than 1m wide. Rosette leaves alternate on the stem and can be up to 60cm long. The leaves are very shiny and have a distinct appearance due to a series of white veins and blotches. Its sharp spines surround large purple flowers, each producing up to 200 seeds.
Why is it a problem?
Variegated thistle is a problem as it is a large invasive plant that can reduce the stock carrying capacity of a property. Dense clumps can kill the grass beneath it, and pasture regeneration is slow. Wilted plants (from being cut or sprayed) become very palatable to cattle. Cattle that gorge themselves on this plant can die within 2 hours from nitrate poisoning.
Control methods
Grubbing can be effective for small or young plants, but it’s important to remove at least the top 5 cm of the taproot.
Variegated thistles can be controlled with a variety of herbicides, but it is best to hit them at rosette stage or seedling stage.
Spraying with glyphosate at 100ml/10l at rosette stage or older or using 24D at rosette stage can work well. MCPA can also work well at label rate.
It’s worth being mindful of using herbicides that may damage pasture or crops.
More information
Variegated thistle is listed as a Sustained Control plant under the Hawke’s Bay Regional Pest Management Plan 2018-2038 and is subject to Plan Rule 18 relating to boundary control.
Management Programme
Sustained Control Programme
To provide for ongoing control of the subject, or an organism being spread by the subject, to reduce its impacts on values and spread to other properties.
Unwanted Organism
An unwanted organism is any organism that's capable of causing harm to natural or physical resources (like forests and waterways) or human health. A number of introduced pests in New Zealand are classed as unwanted.
Rules
Plan rule 18 - Bathurst bur and variegated thistle plants
All occupiers shall, on receipt of a written direction from an Authorised Person, destroy all [NAME] plants within 5 metres of the property boundary, or on land that they occupy where an adjoining occupier is also destroying or the land is clear of, all plants within 5 metres of the property boundary. Council will administer the rule upon receiving a written complaint from the adjacent land occupier and/or at the discretion of the Authorised Person.
Taxonomies
TypePlants
GroupGroundcover
HabitatLand
Management ProgrammeSustained Control ProgrammeUnwanted Organism
RulesPlan rule 18 - Bathurst bur and variegated thistle plants
