A Mandragona as the game calls them are little vegetable creatures that are randomly placed through the universe of Odin Sphere.
When walking along the ground in any given area (or raised platforms) if you see a small black hole and then walk over said hole and hear a noise, this is a Mandragona. You simply need to attack the hole or slide along the ground to uproot one.
They come in a few varieties but the first one you should come across is the Carroteer (it looks like a Carrot, or a really fat Cactrot if you're familiar with the Final Fantasy series). Anyway when you pop one of these out of the ground they begin to run along the ground and away from you. Every so often they will jump and "hit" you if you follow them closely (though they don't take away any of your health by doing this).
Just uproot one and follow it around getting hit whenever you can and before you know it you'll net yourself this trophy.