If you like the combination of strawberries and rhubarb in pie, then this jam is sure to be a winner. Ginger fans should consider adding a cup of chopped crystallized or preserved ginger to the fruit. Raspberries are a great substitute for strawberries as well.
trimmed rhubarb (cut into 1/2-inch-thick slices)
ripe strawberries (stemmed and halved or quartered, depending on size)
fresh lemon juice
fruit pectin (1 box)
Prepare canning jars by washing the jars and screw bands in hot, soapy water. Rinse completely to remove soap residue. Pour boiling water into each jar and let stand until ready to use. Place the flat lids in a bowl of boiling water and let stand in the water until ready to use.
Combine the rhubarb, strawberries, lemon juice, and water in a large saucepan (if you're using ginger, add it here). Bring to a boil over medium-high heat and cook to soften the rhubarb slightly, stirring frequently, about 3 minutes. Add the pectin and bring the mixture to a full rolling boil on high heat, stirring constantly. When a full boil is reached, add the sugar and stir to blend. Once the mixture returns to a full rolling boil, boil for 4 minutes, stirring constantly.
Quickly ladle the hot jam into the sterilized jars, filling to within 1/8 inch of the tops. Wipe the jar rims and threads with a clean cloth, and cover the jars with the lids and screw bands. If you're using a water canner, process the jars according to the manufacturer's instructions. Otherwise, invert the hot jam jars and let rest for 5 minutes. Store the jam in a cool, dark cupboard for up to 6 months. Refrigerate the jam after opening.