| woolly thistle | (n) thistle of western North America having white woolly leaves, Syn. Cirsium flodmanii |
| european woolly thistle | (n) woolly thistle of western and central Europe and Balkan Peninsula, Syn. Cirsium eriophorum |
| cotton thistle | (n) biennial Eurasian white hairy thistle having pale purple flowers; naturalized in North America, Syn. Scotch thistle, woolly thistle, Onopordum acanthium, Onopordon acanthium |