"In general, it's true that you don't want to combine fruit with any other foods...except raw leafy greens!
Raw leafy greens combine well with any food. The digestive enzymes and light live nutrients they contain aid in digestion for any other foods (even fruits)"
For me i think lettuce or spinach or Celery would work fine mixed with fruit, but my stomach didn't like it much when i had strawberries with the tops and also i had a very bad reaction to a papaya/collard greens combo. I have a feeling the food combining exception for "leafy greens and celery" does not include the heavy hitters like kale, collards, swiss chard, and bok choy (and strawberry tops).