Scotch thistle stands are dense and practically impenetrable due to the weed's spiny nature and large size. It spreads by seed and generally inhabits moist sites or drainages in dry locations. The plant forms a rosette of leaves the first year and produces a seed stalk the second year. The entire plant is finely hairy to woolly, giving it a silvery-gray color. Flower heads are borne in midsummer in groups of 2 or 3 on branch tips.
Seeds are slender, smooth, and plumed.