Classed as an injurious weed, spear thistle should not be allowed to spread or seed.
Spear thistle
What is spear thistle?
Spear thistle (Cirsium vulgare) can be found in both newly sown leys and established grassland.
Biology
A biennial that grows from seed, it forms a rosette in the first year and flowers in the second year.
Spear thistles can produce up to 8,000 seeds per plant.
Seeds are dispersed by the wind and can travel up to 30m.
Seed is viable in the soil for up to 3 years.
Plants form rosettes and have a taproot up to 70cm in length and spiny leaves.
In its second year, the plant can grow to over a metre in diameter before flowering, posing a serious economic threat.
Spear thistles flower from July to October and have purple flower heads.
How can I identify spear thistles?
Flowering plant
Rosette stage
Closer look at leaves
Why are spear thistle a problem?
- They compete with grass for space, light, nutrients, and water and are unpalatable to livestock.
- Thistles can facilitate the spread of orf in sheep and lambs. When grazing close to thistles, the spines can traumatise the skin allowing the orf virus to infect livestock.
- In its second year, a spear thistle can cover more than a square metre of ground, thus posing a serious threat to pasture productivity.
- Low infestations of just 1% can justify treatment.
How do I control spear thistle?
Control at the rosette stage, up to 200mm across or high, when plants are young and actively growing.
Uprooting the plant will prevent the spread of seed, although roots may remain.
Topping may be appropriate as a first step treatment to get different growth stages to the same stage ready for treatment with a translocated herbicide.
Use Thistlex® when thistles are the primary target. If other weeds are also present, use Forefront® T or Grazon® Pro/Spot (for spot treatment).
Grazon Pro Herbicide
Grazon® Pro contains a combination of clopyralid and tricopyr that provides excellent control of creeping thistle and spear thistle.
Grazon SPOT Herbicide
Grazon® SPOT is a smaller more convenient 0.5 litre bottle (equivalent to eight 10 litre knapsack fills) is ideal for those treating smaller areas.
Forefront T Herbicide
Forefront® T delivers the highest levels of control of docks, thistles, nettles, ragwort, buttercups and dandelions.
Thistlex Herbicide
Thistlex® is a very effective translocated product for the control of both creeping and spear thistle. It is very safe to grass.