In the video gameThe Witcher 2, you will often hear enemy soldiers shout that sentence. Lilies are the emblem of the kingdom of Temeria. In essence "Plough the lilies" means "Fuck the Temerians"
Used by enemies in the gameThe Witcher 2, can be speculatively translated as, "Fuck the women," as the word "plough" is used as a synonym of the word "fuck." Example: "Go plough yourself!"