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Thistle Nodding

NODDING THISTLE

Carduus nutans
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Thistle-Nodding

DESCRIPTION

Nodding Thistle is a large, invasive thistle that can quickly achieve a dense cover that smothers the pasture beneath. It can reach about 1.5 metres tall, and usually grows in thick patches. It has a distinctive purple, drooping (‘nodding’) flower head that’s easy to identify, but before reaching that stage it might be confused with Scotch and Plumeless Thistles. The leaves of a Nodding Thistle are green and have shiny metallic-looking upper surfaces, usually with whitish edges. The flower stems have narrow, spiny wings growing to just below the flower head. Rosette leaves are long and narrow, and deeply cut with spiny edges.  

Nodding Thistle can be either biennial or annual. One plant can produce 10,000 viable seeds that are easily spread by farm machinery, stock and birds. Seeds germinate mainly in autumn, but can germinate outside that period.  Autumn-germinated plants will flower and seed the following summer. Later germinations remain as rosettes for the first year and complete their life cycle by flowering in their second summer.  

Caution: If you slash Nodding Thistle plants it will make the pasture appear tidy, but it will also prevent them from flowering on schedule, so they will simply remain present in your pasture as perennials until they are able to flower when you’re not looking. So eventually you’ll still have to eradicate them.

PASTURE MANAGEMENT

The best control measure is pasture management, because a tight pasture sward will minimise thistle germination and throttle growth of any thistle seedlings.  However, thistles will usually find some opportunity to establish themselves, and one plant quickly becomes a clump, which soon becomes an infestation. 

GRUBBING-OUT

Individual plants and isolated clumps can be grubbed out successfully before seeding. Take at least 5cm of the taproot to avoid regrowth.

MOWING

Mowing (topping) mature plants can be a useful control, but timing is critical. For best results, mow after flowering, but before seed has set. Plants mowed before flowering will become hard-to-kill multicrown thistles. Plants mowed after seed set will of course multiply via the mass of released seed.

HERBICIDES CONTROL NODDING THISTLES 

Large infestations of Nodding Thistle are best sprayed. The optimum times for spraying are late autumn/early winter or in spring, when the plants are seedlings and more susceptible. If there’s good pasture cover present, graze it well a week before spraying to maximise results and minimise pasture damage.

Boom Spray Herbicides to Kill Nodding Thistles
  • Rainbow & Brown MCPA – 3L/ha on seedlings, 4L/ha on small rosettes with crowns to 4cm diameter. This herbicide will damage clover if present.
  • WHACK – 2,4-D 800 – 2kg/ha for seedlings with root crowns less than 2cm and 2.25-2.7kg/ha on rosettes with root crowns between 2-4cm, before flower stalk develops.
  • Ralid (used alone) – 1L/ha until early flowering. Ralid (Clopyralid) is also an excellent addition – 100-200ml/ha to both Rainbow & Brown MCPA 750 or PastureMate combo where larger, multicrown or otherwise hard-to-kill thistles are present.
  • PastureMate – 4L/ha for good control in seedling stage (2-3 leaves). Useful suppression at later growth stages. This is pasture (grass/clover) friendly.
Spot Spray Herbicides to Kill Thistles (Nodding Thistles)
  • GrassMate – 6m/L applied anytime to whole plant. Grass friendly, but will suppress clover.
  • Ralid – 25ml/10L (knapsack) or 100ml/100L (handgun). Effective anytime against larger plants. To be used only by a qualified handler.
  • WHACK – 2,4-D 800 – 45g/10L covering 250m2 but this may only be effective on smaller thistles.
  • GrassMate XTRA  – 6ml/L by knapsack (Rosette and multi-crowned plants)
Spot Treatment Herbicides to Kill Thistles (Nodding Thistles)
  • Buckshot applied dry at 2g to the crushed centre of each plant. Best applied to smaller plants, but effective against larger plants as well. An excellent option for killing thistles that have survived or been missed in earlier treatments.
Weed Wiper Herbicides to Control Nodding Thistles
  • MSF600 – 2g/L of water.  For faster visible results add G-360 GLYPHOSATE – 250ml/L water, G-540 GLYPHOSATE – 165ml/L water, or Granny Herbicide high strength, granular glyphosate at 110g/L water. Graze to reduce pasture height prior to treatment, so that the wiper can be set as low as possible. Make multiple passes over thick patches. Where a weed wiper can be used, this method is cheap, very effective against even mature & multicrown thistles, and of course is totally pasture-friendly.
Non-Selective Herbicides to Kill Thistle Nodding in non-cropland areas