the farm tiles allow you to grow crops which give you energy or gold, they become available after completing a quest near the end of area 2.
the best part though is that , if you assist the crops someones crops(by clicking on them you gain free energy and gold) and the crops owners wait time is reduced by 1 hour.
who has the farm tiles though?
(you can access their house by adding them as a friend and then clicking on theit picture and the little icon that looks like a plant.)
please reply if you get the crop tiles so i can add you to the list