Pink Tree Field is a field and forest located on the outskirts of Ponyville. The place seems to be a popular relaxation destination, as the Mane Six have gone on picnics there on a number of occasions, and Mayor Mare has relaxed there too.
The Mane Six had a picnic in its gazebo area though Twilight Sparkle left the picnic as soon as she arrived due to the stress of not having a letter to write to Princess Celestia. Her friends didn't take her seriously, causing Twilight to storm off. In another part of the location, Twilight tried to make the Cutie Mark Crusaders get into a fight with each other over Smarty Pants. When the fight didn't occur, she used the Want It Need It spell to make them argue over it. This eventually snowballed into nearly the entire town fighting in the field for the doll.