Citrus fruit is in season in the winter and you can always find frozen blueberries so this is a great pie for the holidays. I use tangelos and navel oranges because I like the taste of tangelos, they're seedless and they sound good in the title. (I've found at the restaurant that a dessert with the word navel in it just does not sell.) If you can't find tangelos use all navel or some satsumas.