• 4 cups (1 lb/500 g) raspberries
• 4 cups (1 lb/500 g) blackberries
• 4 cups (1 lb/500 g) blueberries
• 3 cups (1½ lb/750 g) sugar
• ¾ cup (6 fl oz/180 ml) fresh lemon juice

Have ready hot, sterilized jars and their lids.

In a large nonreactive saucepan, gently toss together the berries, sugar, and lemon juice. Bring to a boil over medium-high heat, reduce the heat to medium, and cook, uncovered, stirring frequently, until the jam has thickened, about 15 minutes. It will continue to thicken as it cools.

Ladle the hot jam into the jars, leaving ¼ inch (6 mm) of headspace. Remove any air bubbles and adjust the headspace, if necessary. Wipe the rims clean and seal tightly with the lids.

Process the jars for 10 minutes in a boiling-water bath (for detailed instructions, including cooling and testing seals, Canning Step by Step). The sealed jars can be stored in a cool, dark place for up to 1 year. If a seal has failed, store the jar in the refrigerator for up to 1 month.