The trees produce food pretty quick, so feeding your pet something cheap or FREE with a little prior investment, you will no longer need to keep buying food from the Food Shop. As for the extra food that you don't eat, you can recycle them in the green bin to get recycle points from 300-600 points depending on the food.
This method helps you save money in the long run so you can buy more stuff with your coins, instead of feeding your pet with expensive food all the time! This method can also be used to help get your recycling trophy as the food you recycle are worth a decent amount of points. Oh, and did I mention the recycling your doing is free?
Save money, food, get points, recycle!