SAFFRON THISTLE
Carthamus lanatus
DESCRIPTION
This is an annual or sometimes biennial thistle, not as widely distributed as some of the more common thistles. It’s an upright thistle, with a typical woody, many-branched stem, and lots of sharp spines.
The flowers appear singly, atop flower stems reaching 50cm in height. They’re bright yellow with some purple veins, and are surrounded by small, leaf-like bracts that turn downwards from the flower. The saffron thistle flowers from Jan–Apr.
Leaves are glossy green, alternately placed on the stem, and have sharp spines perpendicular to the leaf edges. They’re 7-8cm long and about 3cm wide at the base. Rosette leaves have multiple spiny teeth.
The seeds are each topped with silk-like hairs. They’re spread by wind and water, and also transported to fresh sites by animals and farm machinery. Where this thistle is present, the seeds will readily contaminate wool.
The root system is a typical thistle taproot.
The saffron thistle can form very dense stands, impenetrable to stock. Pasture productivity is badly compromised by these thistle stands.
Preferred habitat is any arable area, roadsides and waste areas, and pastures with less than optimum cover. It does well in semi-arid conditions, especially where soil fertility is low.
The saffron thistle is distributed occasionally through the eastern parts of the North Island, and the upper and eastern parts of the South Island.
PHYSICAL CONTROL
The best non-chemical defence is to maintain a vigorous and dense pasture cover, and optimum soil fertility. Individual thistles and small infestations can be successfully grubbed out.
HERBICIDES TO CONTROL SAFFRON THISTLES
Spot Treatment Weedkillers to Kill Thistles (Saffron Thistles)
- GrassMate – 60ml/10L water is an effective treatment for crowned plants.
- BuckShot dry granules applied direct to the centre of rosettes, or around the base of crowned plants.
- WHACK – 2,4-D 800 – 45g/10L will control seedlings.
- GrassMate XTRA – 6ml/L by knapsack (Rosette and multi-crowned plants)
Boom Spray Herbicides to Kill Saffron Thistles
- Rainbow & Brown MCPA750 – very economical at 1.5-3.0L/ha applied at 200-300L spray solution per hectare.
- WHACK – 2,4-D 800 – the higher rate of 2.75kg/ha will control seedlings and rosettes well, with no damage to pasture grasses. Clover damage is minimised where clover is largely dormant, or has been hard grazed shortly before spraying.
- Dicamba 500 Select – 100ml plus 200ml Rainbow & Brown MCPA750 in 200-300 litres of water per hectare.
- Dicamba 500 Select – 200-280ml in 200-300L per hectare. Grass friendly but will kill clover.
- GrassMate – 2L/Ha will control seedlings without grass damage, though it will damage clover if present. Higher rates of GrassMate used for controlling brushweeds in pastures will also control the thistles at all growth stages.
- G-360 GLYPHOSATE – 4L/Ha, or G-540 GLYPHOSATE – 2.65L/Ha, or Granny Herbicide – 1.8kg/Ha, sprayed onto seedling-infested pasture over late autumn-winter. This is not a pasture-friendly solution, but is effective where pasture damage is not a concern.
- Ralid – 100-200ml/Ha in conjunction with either WHACK – 2,4-D 800 or Rainbow & Brown MCPA750 as above, will control large and resistant thistles. Expect some pasture damage, especially to clovers. Ralid used alone at 1L/Ha is also effective, but clover damage will be severe.