Slice rhubarb about 1/3 inch slices. Combine rhubarb and strawberries in a bowl. Mix sugar, flour, cloves, nutmeg, and cinnamon and stir into the fruit. Let stand for about 15 minutes. Stir occasionallty. Pour into unbaked pie crust and top with butter. Make a lattice top crust and bake on lowest shelf at 375' for 35-40 minutes.