What is Milk Thistle? Milk Thistle (Silymarin) is a flowering herb related to the Daisy and Ragweed family. It's native to fertile areas along the Mediterranean and is often referred to as "Holy Thistle" for its prestigious purple appearance. This potent plant has long been valued in wellness for its unique botanical properties. It's often combined synergistically with similar tonic herbs like Dandelion and Yellow Dock.