Prepare six 8-ounce canning jars and their lids and bands for processing following manufacturer’s directions.

Heat jars in canner with enough water to cover to boiling. Meanwhile, in large bowl, with potato masher, crush enough berries in batches to measure 5 cups crushed berries.

In 5-quart Dutch oven, with wire whisk, gradually stir pectin into crushed berries. Let mixture stand 10 minutes. Meanwhile, place lids in small saucepan and cover with water; heat to boiling and set pan aside.

Heat strawberry mixture to boiling over high heat, stirring constantly. Stir in sugar and return strawberry mixture to a rolling boil. Boil hard 1 minute, stirring constantly. Remove strawberry jam from heat. With metal spoon, skim off and discard foam as it accumulates on top.

Place jars and lids upside down on wire rack set over towels to drain. Spoon jam into hot, drained jars to within 1/4 inch from top of jar. Wipe jar rims clean. Seal jars. Process in boiling-water bath for 10 minutes. Remove and let cool on a towel.