Stem and wash plums. For whole plums, prick skins on two sides with a fork to help prevent splitting. Freestone varieties may be halved and pitted.
For hot pack, add plums to water or hot syrup and boil 2 minutes. Cover and let stand 20 to 30 minutes. Fill jars with hot plums and cooking liquid, leaving 1/2-inch headspace.
For raw pack, firmly pack raw plums into jars and add hot water or syrup, leaving 1/2-inch headspace.
Boiling-water process pints 20/25/30/35 minutes and quarts 25/30/35/40 minutes at 0–1,000/1,001–3,000/3,001–6,000/above 6,000 ft.