Combine flour and salt in bowl. Cut in shortening with pastry blender until mixture resembles coarse meal. Sprinkle cold water, 1 tablespoon at a time, over mixture, tossing lightly with fork until pastry just holds together. Divide in half; shape each half into a disk. Wrap in plastic wrap. Chill 1 hour.
Combine strawberries, rhubarb, sugar, tapioca, ginger, cinnamon and salt in large bowl. Let stand 20 minutes.
Heat oven to 375 degrees F.
Roll out half of pastry on well-floured surface to 11-inch circle. Transfer to 9-inch pie pan. Trim pastry even with edge of pan. Spoon filling into piecrust. Dot with butter.
Roll out remaining pastry to 11-inch circle. Place over filling. Make decorative edge. Cut vents in top. Place on foil-lined baking sheet.
Bake in 375 degree F oven 1 hour, until golden. Tent with foil if browning too quickly. Remove to rack to cool. Makes 10 servings.