Interestingly, the ancient forms of Broccoli, Cauliflower and cabbage were all carniverous in some form or other...
I have a picture in my head now of stone-age cabbages stalking the land and eating unwary dinosaurs! Check this link for more information.
At the bottom of the page underneath the picture, the topic is given as "Fakeapedia". It looks like this story is the figment of someone's wild imagination. His style of writing is pretty convincing though.