1) Wash and drain jars. Prepare flat lids and screw bands.

2) Fill canner ½ full of water, simmer water on Low.

3) Get the jars warm/hot: Place jars on rack in the canner; let simmering water keep them warm while cooking jam OR put empty jars on a dish towel-lined cookie sheet; warm in oven at 250°F. for 20 minutes. *Important-only fill warm or hot jars with hot jam (cold/room temp. jars may crack when hot jam is added).

4) Measure total amount of sugar into a huge bowl; it must be added all at once at the right stage of the jam-making process.

Crush marionberries (need 6 cups finely crushed berries- measured AFTER they're crushed! Crush 1 cup at a time, using a potato masher. Add crushed berries to a large (separate) stockpot.

Stir in pectin until combined. Turn heat to HIGH- bring berry mixture to a full rolling boil, stirring constantly. NOTE: A full rolling boil is when it's boiling so hard it doesn't stop bubbling, even when stirred. Once it reaches a full rolling boil, stir in sugar all at once! Stir well to combine and dissolve the sugar.

Bring berry mixture back to a full, rolling boil on High. Once fully boiling, set a timer- boil jam for EXACTLY 4 minutes, stirring constantly. When time is up, remove stockpot from the heat. Skim/discard any foam on top.

Put a dish towel under hot canning jars before filling (helps to catch drips). Ladle hot jam into hot, drained jars using a canning funnel, Leave1/8" (one-eighth inch) headspace in each jar. Insert a plastic knife down into each jar a couple times to remove air bubbles, then adjust headspace to 1/8" (if necessary) by removing or adding jam. Use a damp cloth or paper towel to wipe down rims and edges of each jar (need to be clean so flat lids can seal properly). Add flat lids, then screw on jar rings to fingertip tightness (don't overtighten). Place jars on elevated rack in the canner. 

Lower rack of jars into the simmering water. Jars must be fully covered with water, with at least 1" of water above the top of the jars. Add more boiling water, if necessary so water line is 1" above the top of the jars. Cover the canner. Bring water in canner to a gentle boil. Once water is gently boiling, process jam for 10 minutes. When done, wait 2-3 minutes then remove canner lid (lift it away from you because of steam).

Carefully lift jars out of the water with canning tongs. Set jars on a dish towel to cool (don't put HOT jars directly on the kitchen counter because temperature variances could cause the HOT jars to crack). As jars cool, you should hear a "ping" sound as each jar seals. Let jam cool for 12-24 hours without disturbing. Once cool, check to ensure each jar sealed properly. The jar lid should not spring back when pressed lightly in the middle. If a jar did not seal properly (lid springs or pops back when pushed), you need to refrigerate (and use) that jar of jam because it cannot be safely stored long-term.

Wipe down, then label the jars. Remove the screw band before storing jars. Store jam in pantry for up to a year (or more). Enjoy!