While that's simmering wash and pit the plums. Depending on size cut them either in half or in quarters. For very small plums you can leave them whole, but prick the skins so they don't burst during processing.

After the syrup has simmered for 10 minutes, add the plums. Bring the plums and syrup back to a boil, stirring frequently, and remove from heat.

To each pint jar add 3 cloves and 1 tsp or orange zest. Fish the cinnamon sticks out of the syrup and add one to each jar.

Now add the plums to the jar leaving 1/2" of headspace. Try to fit them in as tightly as possible without squishing them.

Cover the plums with the hot syrup. Remove the air bubbles and top off with syrup as needed, again, leaving 1/2" headspace.

Wipe the rim with a clean cloth dipped in vinegar, and adjust the lid. Fill and close remaining jars.

Process in a boiling waterbath canner for 20 minutes for pints or quarts. Or process in a pressure canner for 10 minutes at 6 pounds pressure for pints or quarts. Whichever canner you use, don't forget to adjust the time or pressure according to the altitude chart.

After processing, allow the jars to cool, undisturbed, 12 to 24 hours. Check the seals before you put the jars in storage.