Nodding thistle
Asteraceae - Carduus nutans
BioSecurity

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 are produced per flower, of which two-thirds are viable. Seed may lay dormant in the soil for up to 20 years.

 

 

Control Methods

Options:

  1. Grub out scattered plants or small infestations; remove at least first 5cm of taproot.
  2. Weed wipe, all year round (300ml glyphosate/1L or 1g metsulfuron/1L).
  3. Spray lightly, not to run off, spring - summer (100ml glyphosate + 20ml penetrant/10L) or winter (3g metsulfuron + 10ml penetrant/10L). Avoid water contamination.
  4. Boom spraying established infestations (2,4-D ethylhexyl ester 2-2.5l/ha).

 

 

More Information

Good pasture management can prevent establishment.

•Prevent overgrazing especially in summer.

•Ensure biocontrol agents are present.

For further information or control advice please contact one of our Biosecurity Officers at the Northland Regional Council on 0800 002 004.

 

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