In the video game The 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"
Barpatron: Look, Temerian soldiers!
Other patron: Plough the lilies!
Ex 1.
Ted - "I'm on level four of the Ramada Inn."
Mark - "Oh really, I'm a phough up."
Ex 2.
Henry - "I'm in room 112."
Julie - "I'm a phough over you should stop by sometime."
Ex 3.
Son - "Turn the radio up a phough."
Mom - "Sure thing."
'Ploughing' refers to a specific type of sexual intercourse where one is entered so powerfully that they feel they are being ploughed. Originates from Alderney and can be used as a casual expression to indicate one's sexual desires or activities. The letters 'DTP' are colloquially and frequently used as a shortened phrase. 'DTFP' is also a common alternative.