. Milk thistle Known by more names than is good for it the Milk Thistle - Silybum marianum is a common weed or flower depending on your point of view. Famous of course as being the flower of Scotland it is also well known for being extremely prickly as anyone who has ever tried picking one will testify. This image is the result of a 00 image focus stack. Milk thistle Known by more names than is good for it the Milk Thistle - Silybum marianum is a common weed or flower depending on your point of view. Famous of course as being the flower of Scotland it is also well known for being extremely prickly as anyone who has ever tried picking one will testify. This image is the result of a 00 image focus stack. 