Rinse cherries, blueberries and blackberries with cold water and drain. Remove stems and pits from cherries. Grind the pulp with a hand blender. Lightly mash the blueberries and blackberries with a fork and sprinkle with juice of one lemon.
Mix the fruits with the jelling sugar in a large saucepan. Bring to a boil over high heat, stirring until bubbling, 4 min.
Remove the saucepan from the stove. Perhaps skim the jam, fill hot to the brim in prepared jars and seal on the spot. Makes 6 jars of 250 ml each.