biennial thistle, muck, plumeless, scotch, bull
Biennial thistles produce seedlings during the summer and fall. Plants overwinter as rosettes and produce a flower stalk the next spring, seed, and die. Musk and plummeless are the most serious of the biennials. They produce a heavy seed crop and seedling vigor is very good. Treatments suggested have provided over 90% control into the next season and have reduced seedling emergence considerably during the next year.
Wrage, Leon J. and Johnson, Paul O., "Biennial Thistle (Muck, Plumeless, Scotch, Bull)" (2002). SDSU Extension Extra Archives. 289.