Onopordum acanthium (cotton thistle or scotch thistle) is a common weed, especially in the Midlands. It is a large spiny plant that is woolly hairy. The flower heads are large (usually several cm wide) and have purple florets. Its relative, O. acaulon, is similar but does not produce an erect stem.

Cirsium vulgare is also sometimes known as scotch thistle.