Step 1

Prepare a boiling water bath canner and enough jars to hold 7 half pints of jam.

Step 2

In a large, nonreactive pot, combine the prepared cherries, crushed blueberries, sugar, and pectin. Stir well to combine.

Step 3

Place the pot on the stove over high heat and bring to a boil. Reduce the heat to medium-high and cook at a boil for 20-25 minutes, stirring regularly, until the jam has reduced by about a third and has thickened (here's my favorite way to test for set).

Step 4

When the jam is finished cooking, remove the pot from the stove. Take one jar from your canner. Place it on a wooden board or towel-lined countertop and fit it with a wide mouth canning funnel. Fill the jar with jam, leaving 1/4 inch headspace. Wipe the rim with a clean, damp cloth and fit the jar with one of your clean lids. Secure the lid in place with a ring, taking care to not overtighten.

Step 5

Return the filled jar to the canner and repeat the filling process with the remaining jars.

Step 6

Process the filled jars at a full, rolling boil for ten minutes. When the time is up, turn off the heat, remove the lid, and let the jars cool in the pot for five minutes.

Step 7

When that cooling time is up, remove the jars from the canner and set them to cool on a wooden cutting board or folded kitchen towel.

Step 8

When the jars are completely cool, remove the rings and check the seals. Sealed jars are shelf stable for at least a year. If any jars did not seal, refrigerate them and use promptly.