Blackberries and blueberries can be frozen. To retain blueberries’ maximum flavor, cook them while they’re still frozen; blackberries taste better if they’re thawed before they’re prepared. To freeze the berries, first wash and then drain them. Spread the berries in a single layer on a parchment-lined cookie sheet, and place them in the freezer. Once they’re frozen solid, they can be stored in an airtight container for up to six months.
Dated Storage Container
Martha Stewart: The Catalog for Living