Blueberry Lemon Jam

6 cups blueberries
3 1/2 cups sugar
1/4 cup lemon juice
2 tsp. finely grated lemon rind

Fill boiling water canner with water. Place 5 clean 250 mL mason jars in canner and sterilise for 10 minutes.
In large stainless steel or enamel pot, crush 3 cups blueberries with a potato masher. Add remaining berries, sugar, lemon juice and lemon rind.
Bring to a boil over medium-high heat and boil for 15 to 20 minutes or until thick, stirring often.
Skim off any foam.
Place lids in boiling water and boil 5 minutes to soften seal.
Ladle jam into hot jars to within 1/4" of top rim. Remove air bubbles with a rubber spatula. Readjust headspace to 1/4".
Wipe jar rims to remove stickiness. Centre lids on jars and apply screwbands. Place jars in canner.
Cover canner and return water to a boil. Boil rapidly for 10 minutes. Remove jars and cool for 24 hours. Check seals, they should curve downwards.

Makes 4 to 5 - 250 mL jars

Adapted from Well Preserved by Mary Anne Dragan, Whitecap Books