Use deep coloured, mature fruit of ideal quality for eating fresh. An average of 1 1/2 to 2 1/2 lb (1 kg) fresh plums is needed for each 1 L jar canned.
Ingredients:
Plums
Sugar syrup or unsweetened fruit juice (apple or white grape) or water
Stem and wash plums. To can whole, prick skins on two sides of plums with fork to prevent splitting. Freestone plums may also be halved and pitted, if desired.
Plums may be canned in water, fruit juice or sugar syrup. Prepare syrup in canner batch quantities—approximately 5 cups (1250 ml) for 7-500 ml jars, according to chart. In large stainless steel saucepan, combine water and sugar for desired syrup type (see chart); bring to a boil. If using water or fruit juice, place juice or water in saucepan; bring to a boil.
Syrup for 7 – 1 L jars
Syrup Type Water Granulated sugar
Very light 10 -1/2 cups (2625 ml) 1- 1/4 cup (300 ml)
Light 9 cups (2250 ml) 2- 1/4 cups (550 ml)
Medium 8- 1/4 cups (2050 ml) 3- 3/4 cups (925 ml)
Add plums to boiling liquid; bring back to a boil; boil 5 minutes. Remove from heat; cover saucepan and let stand 20 to 30 minutes. Remove plums from syrup; return syrup to a boil.
Pack plums into a hot jar to within 3/4 inch (2 cm) of top rim. Add hot liquid to cover plums to within 1/2 inch (1 cm) of top of jar (headspace). Using nonmetallic utensil, remove air bubbles and adjust headspace, if required, by adding more plums and hot liquid. Wipe jar rim removing any food residue. Centre sealing disc on clean jar rim. Screw band down until resistance is met, then increase to fingertip tight. Return filled jar to rack in canner. Repeat for remaining plums and hot liquid.
Jar Size Time
500 ml20 minutes*
1 L 25 minutes*
When processing time is complete, remove canner lid, wait 5 minutes, then remove jars without tilting and place them upright on a protected work surface. Cool upright, undisturbed 24 hours; DO NOT RETIGHTEN screw bands.
After cooling check jar seals. Sealed discs curve downward and do not move when pressed. Remove screw bands; wipe and dry bands and jars. Store screw bands separately or replace loosely on jars, as desired. Label and store jars in a cool, dark place. For best quality, use home canned foods within one year.
Borrowed from: https://www.bernardin.ca/recipes/en/plums.htm?Lang=EN-US