How to Make Plum Jam in Canada (Bernardin Method)

Plum jam is the September preserve that requires the least technique. Plums bring their own pectin, their own acid, and their own colour — you just have to halve, pit, and cook. No peeling, no commercial pectin, no special equipment.

This guide covers the Bernardin water-bath method. The processing time below is the standard Bernardin time; verify against your edition and altitude band.

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Pick your plums

The plum variety changes the jam significantly. The Canadian options:

Italian prune plums (Stanley) — the default

Late-August to mid-September across Canada. Small, oval, deep purple-blue, freestone (pit comes out clean), thin skin, dense flesh. Highest pectin of any common Canadian plum. Makes a deep purple-red jam with reliable set. The recipe in this article assumes Italian prunes.

Burbank plums

Mid-August. Round, red-purple, juicy, sweet. Slightly lower pectin than Italian; jam sets but is softer.

Methley plums

Early-August. Dark red, very juicy, sweet. Use 50/50 with Italian prunes for best results.

Japanese plums (Santa Rosa, Beauty)

Sweet, red-fleshed, low pectin. On their own they make limp jam; mix 50/50 with Italian prunes.

Prairie hardy plums (Pembina, Brookgold, Brookred, Patterson Pride)

Bred at Morden (Manitoba) and Brookings (South Dakota) research stations for zone 3-4 winters. Used widely across Prairie provinces. Variable pectin levels by variety — Pembina and Brookred are high; Brookgold is moderate. Use them where you have them; results are slightly less consistent than Italian prunes but the flavour is genuinely regional.

Wild Canadian plums

Prunus nigra (Canadian plum) and Prunus americana (American plum) grow wild across southern Canada. Smaller, tart, more pectin than any cultivated variety. Excellent for jam but you may need to add a bit more sugar to balance the tartness.

What you need

• 2 kg ripe Canadian plums — yields about 6 × 250 mL jars
• 4 cups granulated sugar (less than peach jam; plums are tarter)
• 2 tbsp bottled lemon juice — for safe acidity guarantee
• Optional: ½ tsp butter to reduce foam
• Bernardin 250 mL regular-mouth jars, fresh SNAP lids, bands
• Standard canning kit — jar lifter, headspace tool, funnel, water-bath canner, ladle, large heavy pot, paring knife
• Frozen plates for the cold-plate test

Method

Step 1: Halve and pit

1. Wash plums under cool water. Pat dry.
2. Score around the stem-blossom equator with a paring knife.
3. Twist the two halves apart. For Italian prunes this works cleanly; for clingstone varieties you may need to cut the flesh away from the pit.
4. Remove pits. Reserve a few for stock if you make plum syrup (the pits contain natural amaretto-like flavour).
5. Chop the halves into ¼ to ½-inch pieces — small enough to spread, big enough to see.

Don’t peel. Skins stay on. They will integrate into the jam and add colour.

Step 2: Combine and rest

1. In a large heavy pot combine the chopped plums, sugar, and lemon juice.
2. Stir to coat.
3. Let sit 30-60 minutes at room temperature. The sugar pulls juice out of the plums, creating syrup. Skip this step and the jam needs more added water to start.

Step 3: Cook

1. Place the pot over medium heat, stirring frequently as the sugar dissolves and the plums release more juice.
2. Once the sugar is fully dissolved, increase heat to medium-high.
3. Bring to a vigorous boil.
4. Boil 25-35 minutes, stirring more frequently as it thickens. The plum skins will start to fall apart and disappear into the jam. Foam will form; skim periodically.

Step 4: Cold-plate test

Starting around 25 minutes:

1. Drop ½ tsp of hot jam on a frozen plate.
2. Wait 1 minute.
3. Push edge with fingertip:
   • Wrinkles, holds shape → done. Remove from heat.
   • Slides smoothly but gels at edge → 3-5 more minutes.
   • Liquid like syrup → 5-7 more minutes, test again.

Plum jam tends to set quickly once it starts — don’t over-shoot, or it gets gummy. The first wrinkle test is your signal.

Step 5: Jar and process

1. Have your water-bath canner simmering with enough water to cover jars by 2.5 cm.
2. Have hot jars ready, fresh SNAP lids on the counter.
3. Stir the jam to redistribute fruit (it tends to settle).
4. Ladle hot jam into hot jars. Leave 6 mm (¼ inch) headspace.
5. Run the headspace tool down inside each jar to release air bubbles.
6. Wipe rims with a damp clean cloth.
7. Apply fresh SNAP lids fingertip-tight.
8. Process in the boiling water bath for 10 minutes at sea level (verify with your Bernardin edition).
9. Adjust for altitude per our altitude-adjustments guide.
10. Cool 12-24 hours undisturbed on a towel. Check seals.

If a jar doesn’t seal: the 24-hour rule applies.

Storage

• Cool, dark, dry place at room temperature
• Best quality 18-24 months
• After opening: refrigerate, use within 3-4 weeks
• Plum jam darkens slightly over time — normal and safe

Variations

Plum-cinnamon jam

Add 1 cinnamon stick to the cooking pot (remove before jarring) or 1 tsp ground cinnamon at step 2. Warm, autumnal.

Plum-ginger jam

Add 2 tbsp finely grated fresh ginger to the plums at step 2. Slight kick.

Plum-cardamom jam

Add 4-5 lightly crushed green cardamom pods (remove before jarring) at step 2. Sophisticated, Indian-Canadian and Scandinavian-Canadian touch.

Italian prune plum brandy jam (refrigerator only)

Add 2 tbsp brandy or amaretto at the end before jarring. Do not water-bath can. Refrigerator or gift jars only, used within a month.

Mixed plum jam

Use 50% Italian prune + 50% other plums (Japanese, prairie hardy). The Italian prunes guarantee the pectin set; the other plums add varietal complexity.

Plum butter (longer cook, no chunks)

After step 3, continue cooking another 1-2 hours uncovered to reduce by half. Puree with an immersion blender. Same water-bath processing. Spread like apple butter; pair with cheese.

How to use plum jam

• On toast or scones — the obvious daily use
• Glaze for roast pork or duck — brush in the last 15 minutes of roasting
• Filling for thumbprint cookies and tarts
• Cheese plate — pairs especially well with sharp cheddar, aged gouda, blue cheese
• PB&J variant — peanut butter and plum jam is underrated
• Stirred into yogurt with a sprinkle of granola
• Crepe filling with crème fraîche
• Sandwich condiment with cured meats and grainy mustard
• Plum jam thumbprint shortbreads — Christmas baking standard in many Canadian-European households

Common problems

• Jam set too firmly (gummy). Over-cooked. Three salvage options: dilute with hot water and stir to loosen; use as a glaze instead of a spread; warm jars gently in hot water before serving. Next batch, stop at the first wrinkle test.
• Jam too soft. Under-cooked or low-pectin varieties. Reboil with 1 tbsp lemon juice for 5 more minutes; redo cold-plate test.
• Plum skins visible as chewy strips. Variety has thick skins; either chop finer next time or blanch-and-peel the plums before chopping (rare for Italian prunes).
• Jam colour is dull brown not purple. Overcooked or stored in light. Stop earlier; store dark.
• Foam stayed in the jam. Skim better next time or use ½ tsp butter trick.
• Fruit floated to top. Stir between ladling jars or let jam cool 5 minutes before jarring.
• Jar didn’t seal. The 24-hour rule.
• Crystals after months. Sugar recrystallization. Warm jar gently to redissolve.

Yield expectations

• 2 kg whole plums → 6 × 250 mL jars (no-pectin path)
• 2 kg whole plums → 7-8 × 250 mL jars (with commercial pectin — shorter cook = higher yield)

A typical Canadian household goes through 6-12 × 250 mL jars of plum jam per year. Scale accordingly.

Why plum jam is worth making

• The most reliable Canadian jam — Italian prune plums almost always set without intervention
• Genuinely regional — Niagara, Okanagan, prairie, and Quebec all produce excellent plums
• No commercial pectin required — heritage technique with stable results
• Heritage Canadian recipe — Mennonite, Ukrainian, Polish, French, and English Canadian traditions all have plum-preserve recipes
• Best gift jar — deep purple-red is the prettiest jam colour on the shelf

Next steps

• How to make strawberry jam — the gateway recipe
• How to make peach jam — August counterpart
• How to make rhubarb jam — June starter
• Why didn’t my jam set — troubleshooting
• Canning altitude adjustments — required reading
• Water-bath canning pillar — broader method
• Coming next: canned peaches in syrup