Combine pureed plums and Gentle Sweet in a saucepan over medium heat. Soften gelatin in water for 5 minutes. Set aside. Bring plums mixture to a gentle boil for 3 minutes. Add softened gelatin. Whisk well. Bring to a boil. Pour into prepared jars. Add lids and rings and seal. 3 1-cup jars of jam. This jam needs to be refrigerated to set properly with gelatin. I store the jars in my fridge after they are sealed.
This jam can be hot water bathed to keep it shelf stable. Place jars in a canner with 1 inch water covering the top of the jars. Bring to a gentle boil for 10 minutes. Remove from the canner and allow to cool.