Canada thistle (Cirsium arvense), bull thistle C. vulgare), musk thistle (Carduus nutans) and several other thistles are common lawn weeds in some parts of the U.S. Most germinate in the spring and grow into a flattened rosette that looks like a large, spiny dandelion and is painful to touch. The rosette dies in the fall, but the thick root survives and sprouts the following spring into an upright spiny plant. Most thistles are problems in new lawns or lawns that are thinning from some other problem, especially drought.
It is difficult to control thistles by digging because any pieces of root left in the soil will re-sprout.