Bull thistle, Cirsium vulgare Tenore, is a Eurasian weed which was accidentally introduced into the United States from Europe during the 1800's. It has since spread through out North Carolina by airborne seed or by transport of seed contaminated hay. It is now of considerable economic importance because livestock will not feed near it and, in moderate infestations, bull thistle can reduce pasture yields significantly. Mature leaves are less than ten inches long and moderately to coarsely lobed, with each lobe ending in a stiff yellow spine. Leaves are alternately attached along the stem.
Stems are hairy and branched.
One or several small, purple flowerheads terminate the branches. Flower bracts are somewhat hairy and tipped with long, sharp spines. The life cycle of bull thistle in North Carolina is variable. It is generally classed as a biennial, but can develop as an annual or winter annual depending on local environmental conditions. Bull thistle reproduces entirely by seed.