Why Control Thistles?
Thistles need controlling because:
● They compete with grass for space, light, nutrients and water
● They are unpalatable to stock
● They lead to greater incidence of Orf
● Reduce the available grazing.
Biology of Thistles
There are 150 species of thistles worldwide, with 20 species in the UK. The two most common and damaging are creeping thistle – Cirsium arvense – and spear (Scotch) thistle – Cirsium vulgare.
Creeping Thistle (Cirsium arvense):
A perennial that grows from seed or from root sections in the soil. Once established, the root mass can be greater than the plant above ground, competing effectively with the grass.
Spear Thistle (Cirsium vulgare):
A biennial that grows from seed, and in the first year often goes unnoticed, since it produces only a small rosette. In the second year the plant can grow to over a metre in diameter before flowering, posing a serious economic threat.
Spear Thistle (Scotch)