Cirsium arvense
Other serious pasture and crop land plant pest are nodding thistle ("Carduus nutans"), Californian thistle ("Cirsium arvense"), ragwort ("Senecio jacobaea"), broom ("Cytisus scoparius"), giant buttercup ("Ranunculus acris"), fat-hen ("Chenopodium album"), willow weed ("Polygonum persicaria"), and hawkweed ("Hieracium" species).