Preheat oven to 375-degrees F
Line the bottom of a 9" pie plate with one of the two pie crusts.
If using frozen fruit, let the mixture stand for 30 minutes or until partially frozen.
Mix mulberries with orange zest, and orange juice.
In another bowl, mix sugar, flour, and salt.
Stir flour into the mulberry mixture.
Pour the mulberry mixture into the prepared pie crust.
Dot with butter, and top with the remaining pie crust, in a lattice fashion.
Cover pie edges with foil or pie crust protectors. Bake for an hour, or until the mixture is bubbly and begins to ooze out of the lattice crust.
Cool before slicing. Enjoy with some vanilla ice cream.