Wash the plums and put them into a large pot. Then add sufficient water to cover the fruit.

Bring the water to simmering and let the plums cook until they are soft and have released their juice. You can expect this to take about twenty minutes.

Strain the fresh juices through cheesecloth or a jelly bag.

In a large pot, combine the plum juice and pectin. Bring the mixture to a rolling boil.

Stir in the sugar. Then return to a full rolling boil. Boil hard for one minute. stir the jelly constantly.

Remove from plum jam from the heat and skim off any foam.

Ladle the hot plum jam into hot sterilized jars. Be sure to leave a 1/4-inch headspace. Be sure you boiled the lids according to instructions on their package. Adjust two-piece caps.

Process the canning jars for ten minutes in a boiling water bath canner.