Cornfields, their floops mainly low enemies defense or raise their attack up. As time passes, flooping them a lot, you can low enemies defense to a little number and raise your attack up to a really great number.
The appearance of their cards is usually simply creatures made of corn or with a farm theme. Its predominant colors are yellow and green.
Note: this is Jake's favorite landscape in the episode "Card Wars" (Season 4, Episode 14 of Cartoon Network's 'Adventure Time.')