From PinataIsland.info, the Viva Piñata wiki
Trees (or seeds to grow them) can be purchased from Costolot's General Store.
General fruit uses
- Eating any piece of fruit helps meet the White Flutterscotch Romance requirements.
- Eating any two pieces of fruit helps meet the Buzzlegum Romance requirements.
- Eating any three pieces of fruit helps meet the Raisant Residence requirements.
General tree uses
- 1 fruit tree of any kind helps meet the Raisant Visit requirements.