Blueberry and Apple Jam

• 1 pound Granny Smith apples (about 3 small)
• 2 pounds blueberries, rinsed

Prepare for water-bath canning: Sterilize the jars and keep them hot in the canning pot, put a small plate in the freezer, and put the flat lids in a heatproof bowl. (details.)

Peel, core, and dice the apples, reserving the peels, cores, and seeds. Put as many of the apple trimmings in a jelly bag or 4 layers of cheesecloth as will f