Wash and cut the plums into chunks, removing the pits.
Combine the plums, water, lemon juice and sugar in a large saucepan. Bring to a boil to dissolve the sugar, stirring continuously.
Continue to stir for 15-20 minutes, or until the gelling point has been reached.
Remove from the heat and ladle into glass mason jars. Proceed with the boiling water canning method, if desired. If not, store the plum jam in the refrigerator.
