I should have known this...

https://www.inaturalist.org/observations/75623580#activity_comment_f31ddd0e-ae03-442f-ae42-c0815a3cab26

Also, with thistles, their relatives, and Asteraceae as a whole, please try to get a good photo of the phyllaries (which you can do with a side-view of the flower head)! The phyllaries are often one of the best features for ID.