Crush the thawed blueberries and measure 4 cups.

Combine blueberries, lemon juice, and pectin in a large pot.

Bring to a full rolling boil, stirring constantly.

Add all 5 cups sugar at once.

Bring back to a rolling boil and boil hard for 1 minute, stirring constantly.

Remove from heat and skim foam.

Ladle into hot jars, leaving 1/4 inch headspace.

Process in a boiling water bath for 10 minutes (up to 1,000 feet elevation), adjusting for higher elevations.

Cool undisturbed for 12-24 hours and check the seals.