What does it look like?
Nodding thistle is a biennial plant that grows from over-wintering rosettes and has a long, fleshy taproot. The flowering stems grow up to 1.5m tall bearing red-purple or, occasionally, white flowers that droop or nod when mature. Sharp spines densely cover the stems and leaf margins.
Nodding thistle is predominantly a weed of pasture (particularly pasture grazed by sheep) and also invades roadsides, wasteland and crops such as lucerne. It will grow in most soil types but does not grow well in excessively wet, dry, or shady conditions and does best under higher soil fertility.
Why is it a problem?
Nodding thistle is considered to be the most aggressive thistle in New Zealand. It can invade pastures at all stages of development, particularly those grazed by sheep, and quickly establish in pastures suffering from summer drought. Its main economic impact is that it prevents stock from eating plants growing in the vicinity of the thistle, replaces desirable vegetation, and hinders stock movement.
Nodding thistle is a prolific seeder, with approximately 200 seeds produced per flower, of which two-thirds are viable. Seed may lay dormant in the soil for up to 20 years.
Control methods
Physical control
Grub out scattered plants or small infestations; remove at least first 5cm of taproot.
Herbicide control
Young seedlings may be sprayed with MCPB without any damage to pasture. Once rosettes get older, MCPA or 2,4-D will be needed, and these can cause suppression of clover growth following spraying.
Boom spray established infestations with 2-2.5lL /ha 2,4-D ethylhexyl ester before September.
Pasture management
Good pasture management can prevent establishment. Prevent overgrazing especially in summer and ensure biocontrol agents are present.
CAUTION: When using any herbicide or pesticide, PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.
Biological control
The nodding thistle receptacle weevil is widespread in Hawke’s Bay as is the nodding thistle gall fly.
More information
Nodding thistle is listed as a Sustained Control pest under the Hawke’s Bay Regional Council Regional Pest Management Plan 2018-2038.
Nodding thistle is subject to Plan Rule 18 as a Boundary Control Plant.
Related links
http://www.nzpcn.org.nz/flora_details.aspx?ID=3633
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.
Rules
Rule 18 - nodding thistle and ragwort plants
All occupiers shall, on receipt of a written direction from an Authorised Person, destroy all plants within 20 metres of the property boundary, on land that they occupy where an adjoining occupier is also destroying or the land is clear of, all plants within 20 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
FamilyAsteraceae
TypePlants
GroupGroundcover
HabitatLand
Management ProgrammeSustained Control Programme
