Pick through your pineberries carefully, remove the hulls, and rinse your berries with cool, clean water.  

Mash your pineberries in a bowl using a masher or durable spoon.  Measure out 8 cups of mashed fruit.

Place the pineberry mash, sugar, and lemon juice into a large saucepan.

Over medium-high heat, cook the fruit mixture, stirring often to dissolve the sugar, bringing the jam to a slow boil.

Cook the mixture at a slow boil, stirring often.  Foam can be skimmed off the top of the mixture with a metal spoon.

Cook the jam until it has reached the gel stage, which should be approximately 45 minutes or a little longer.

Test the jam to see if it has reached the gel stage using the cold plate test or until the temperature reaches the gel stage at 220° F.

Ladle or pour the jam into prepared jars or containers.

Preserve the jam using a hot water bath canning method, or after the jam has cooled, keep the jam refrigerated for up to 1 month or frozen for up to 6 months.