Blueberry Plum Jam -Katy

2 pints blueberries
2 lbs. plums
1/2 cup water
4 cups sugar
1 box sure-jell
1 tsp. butter

Wash blueberries. Pit plums. Chop down fruit, or use a blender or food processor. Put fruit and water in a pan and bring to a boil. Reduce heat and simmer 5 minutes. Measure 1/4 cup sugar and mix with sure-jell; stir then stir in remaining sugar. Return to full boil and boil for 1 minute, stirring constantly. Remove from heat, pour into jars and process 10 minutes in water bath canner.