Prepare a boiling water bath and 3 pint jars. Place the lids in a small saucepan of barely simmering water. (See my water bath canning tutorial for more guidance.)

Place the blueberries in a large pot and use your hands or a potato masher to smash them. You should have 6 cups smashed blueberries. Add the sugar, place the pot over high heat and bring to a boil. Add the lemon zest and juice, cinnamon and nutmeg and cook for 15-20 minutes, stirring frequently, until the jam is shiny and thick. Add the pectin and continue boiling for 5 minutes.

Remove the pot from the heat and ladle your jam into the prepared jars, leaving ½-inch of headspace. Wipe the rims, apply lids and rings and process in a boiling water bath for 10 minutes.