Plum jam needs no bought pectin, as long as the plums are sharp-tasting and not overripe. This tested recipe uses chopped plums, sugar, water and a little lemon juice, boiled hard to setting point and sealed in a boiling-water bath. Damsons make an even simpler version with no lemon at all, given further down.
- Makes
- about 8 jars of about 250 ml (the damson version makes about 6)
- Keeps
- about a year unopened in a cool, dark place after the water bath; once opened, in the fridge for a few weeks to a month or two
- Ready to eat
- once cool and set
- In season
- plums from mid to late summer into early autumn, depending on variety; damsons from late summer, depending on variety and where you garden
Ingredients
- 1.9 litres (about 1.8 kg of plums) tart plums, stoned and chopped, then measured in a jug
- 1.2 kg granulated sugar
- 355 ml water
- 60 ml lemon juice
Measure the stoned, chopped fruit in a jug (about 1.8 kg of plums should be enough to pick), and keep all four amounts exactly as given.
Method
- Sterilise the jars: a hot dishwasher cycle, 10 minutes in boiling water (add 1 minute for every 300 m of height above the first 300 m), or the oven at 160°C (gas mark 3) for 10 minutes. Check the jar maker's instructions; some (Kilner, for example) advise against the oven for their jars. Use new lids, prepared as their maker says (see the sterilising guide).
- Chill two or three small plates in the freezer for the setting test.
- Sort the plums and set aside any that are rotten, overripe or have a grub inside.
- Cut each plum open, take out the stone and chop the flesh.
- Measure 1.9 litres of chopped fruit into a large, wide pan.
- Add the sugar, water and lemon juice.
- Bring slowly to the boil, stirring now and then, until the sugar has dissolved.
- Boil rapidly, stirring constantly so the jam doesn't stick or burn.
- Boil to setting point, about 104.5°C at sea level, for a firm jam, or stop just short of it for a softer one; never cut the sugar to get a softer jam (see the setting point guide).
- Take the pan off the heat and skim off any foam quickly.
- Fill the hot jars with the hot jam, leaving about 6 mm (¼ inch) of space at the top.
- Wipe the rims with a clean, damp piece of kitchen paper.
- Put the new lids on straight away.
- Stand the jars on a rack in a deep pan, cover them with hot water by at least 2.5 cm, bring to a full boil and boil for the time in the water-bath table below: 5 minutes for jars sterilised by boiling, if you live below about 300 m (1,000 ft).
- Lift the jars out upright and leave them to cool undisturbed for 12 to 24 hours.
- Press the middle of each lid. If it springs back up, that jar hasn't sealed: keep it in the fridge and treat it as an opened jar.
Which plums to use
The one plum that never sets on its own is the Italian prune type, which always needs added acid, pectin or both. The recipe above is written for tart plums. If yours are sweet and fully ripe, or prune types, use a tested plum jam recipe with added pectin instead, and use exactly the pectin it names. The pectin guide shows how plums and damsons compare with other garden fruit.
Ripeness matters as much as variety. Pectin is at its best in fruit that is just ripe and falls away as fruit ripens further, so jam plums are better a day early than a day late.
The damson version
Damsons are slightly tart raw but rich once cooked, and they set with sugar and water alone. They have their own quantities, with less sugar than the plum version, so don't put damsons into the plum recipe.
| Ingredient | Damson jam |
|---|---|
| Damsons, stoned and coarsely chopped | 1.2 litres (about 900 g of fruit) |
| Granulated sugar | 600 g |
| Water | 175 ml |
| Lemon juice | none |
| Makes | about 6 jars of about 250 ml |
The method is the same as steps 1 to 16, with one difference: stir now and then until the sugar dissolves, then stir often once the jam starts to thicken. Stone the damsons raw, before you measure them. The stones are fiddly, so allow time for step 4.
Getting a set
A thermometer is the most dependable test. Jam sets at about 104.5°C at sea level and about 1°C lower for every 300 m of height. The cold plate test is a good cross-check: take the pan off the heat, put a little jam on a chilled plate and push it with a finger after a minute. If it wrinkles, it's ready. Jam thickens as it cools, so a set that looks slightly loose in the pan is often right.
Keep the batch to the size given. Small batches boiled hard reach setting point sooner, and a tested recipe shouldn't be doubled. If a batch stays soft, the usual causes are not boiling long enough, too big a batch or overripe fruit. The setting point guide covers what to do next.
Sugar and lemon
Sugar is the preservative in jam. It stops microorganisms growing, adds flavour and helps the gel form. Cut it and you get a runny jam that spoils sooner. The lemon juice supplies acid, which the set needs. Keep every amount as written. For a less sweet jam, use a tested recipe written for reduced sugar.
The water bath and keeping the jars
These recipes were tested with the boiling-water bath in step 14, and their keeping time depends on it. The bath time depends on how the jars were sterilised and how high you live; if you garden in the hills, check your height before choosing a time.
| Jars sterilised by | Home below about 300 m | Home above about 300 m |
|---|---|---|
| Boiling for 10 minutes | 5 minutes | 10 minutes |
| Dishwasher or oven | 10 minutes | 10 minutes, plus 1 minute for every 300 m (1,000 ft) above sea level |
Keep the water boiling for the whole time. If it stops, bring it back to a full boil and start the timing again. Jars that are only filled hot and lidded have no tested keeping time: store them in the fridge and eat them soon. Waxed discs and cellophane covers don't replace new lids and the bath. The jars guide helps you choose jars and lids.
If you live above about 300 m, three things change:
| At height | What changes |
|---|---|
| Sterilising jars in boiling water (step 1) | 10 minutes, plus 1 minute for every 300 m above the first 300 m |
| Setting point (step 9) | About 1°C lower for every 300 m |
| Water bath (step 14) | See the table above |
Water-bathed jars keep for about a year in a cool, dark, dry place. Once a jar is open, keep it in the fridge and use it within a few weeks to a month or two. Throw out any jar with mould, or a fermented, yeasty or alcohol smell; don't scrape the mould off and eat the rest. The preserve storage guide has more detail.
From tree to pan
Plums and damsons ripen gradually, so a tree needs picking over several times. That suits jam: pick the fruit that's just ripe, make a batch, and come back for the next lot a few days later. Ripe fruit feels soft when gently squeezed. Handle it gently, as it bruises easily.
The first plums to ripen are the likeliest to hide a pinkish plum moth caterpillar, with brown droppings near the stone. Fruit ripening later on the tree is usually much less affected. Cutting every plum open in step 4 shows you which ones to leave out. Take brown-rotted fruit off the tree and the ground promptly too, so the rot doesn't carry over.
The plum growing guide and the damson growing guide cover varieties and care. When the tree crops faster than you can make jam, dealing with a glut of plums has other ideas, and spiced damson chutney uses up a big damson crop.
Common questions
Can I use Victoria plums?
This recipe is written for tart plums. For sweet, fully ripe dessert plums, use a tested plum jam recipe with added pectin, and follow it exactly.
Can I use plums in the damson recipe, or damsons in the plum recipe?
No. Each is a separate tested recipe with its own balance of fruit, sugar, water and acid. Use the one written for your fruit.
Why is my plum jam runny?
It may just need time, because jam firms up as it cools; leave the jars unmoved for at least 12 hours before judging. Otherwise the usual causes are not boiling long enough, too big a batch or overripe fruit. The setting point guide covers what to do next.
Can I skip the water bath?
Only if you keep the jars in the fridge and eat them soon. The year's keeping time applies only to jars that have been through the bath.
Sources
Show the 23 sources
- Recipe proportions based on: Plum Jam without Pectin (National Center for Home Food Preservation, University of Georgia): Ingredients (2 quarts chopped tart plums, about 4 pounds; 6 cups sugar; 1½ cups water; ¼ cup lemon juice), yield (about 8 half-pint jars), method (sterile jars, bring slowly to boiling until sugar dissolves, cook rapidly to or almost to the jellying point of 220°F at sea level, stir constantly), ¼-inch headspace, wipe rims, boiling-water process 5 minutes at 0–1,000 ft and 10 minutes at 1,001–6,000 ft
- Recipe proportions based on: Damson Plum Jam without Pectin (National Center for Home Food Preservation, University of Georgia): Ingredients (5 cups coarsely chopped damsons, about 2 pounds; 3 cups sugar; ¾ cup water; no lemon or pectin), yield (about 6 half-pint jars), method (stir occasionally until sugar dissolves, cook rapidly, stir frequently as it thickens), ¼-inch headspace, boiling-water process 5 minutes at 0–1,000 ft and 10 minutes at 1,001–6,000 ft
- Plum Jam with Pectin (National Center for Home Food Preservation): A tested plum jam with added powdered pectin, made from fully ripe plums (referred to, quantities not given)
- Jellied Product Ingredients (National Center for Home Food Preservation): Non-Italian plums in Group I (set with sugar alone if not overripe); Italian plums in Group III (always need added acid, pectin or both); acid needed for the gel; sugar as preservative; never cut the sugar; best pectin in just-ripe fruit
- Making Jams, Jellies and Fruit Spreads, SP 50-764 (Oregon State University Extension): Sour plums listed as high in pectin and acid
- Jams and Jellies from North Dakota Fruits, FN590 (NDSU Extension): The riper the fruit, the less pectin it contains
- Basics of Jelly Making (Clemson Cooperative Extension HGIC): Sugar preserves, flavours and aids gelling; non-Italian plums in Group I
- Making Jam without added Pectin (National Center for Home Food Preservation): Remove pits and cut fruit into pieces; cold plate test; allow for thickening during cooling; remove from heat and skim foam quickly
- Testing Jelly Without Added Pectin (National Center for Home Food Preservation): Temperature test most dependable; 220°F (about 104.5°C) at sea level; 2°F lower per 1,000 ft (about 1°C per 300 m)
- Causes and Possible Solutions for Problems with Jellied Fruit Products (National Center for Home Food Preservation): Causes of a soft set (undercooking, too little acid, too large a batch); small batches cooked rapidly; don't double tested recipes; plum jellies can take up to 2 weeks to set; mould or fermentation means don't use
- General Information on Canning Jams, Jellies, and Marmalades (National Center for Home Food Preservation): Water bath 5 minutes with sterile jars, 10 minutes with unsterile jars, plus 1 minute per 1,000 ft of elevation; ¼-inch headspace
- Sterilization of Empty Jars (National Center for Home Food Preservation): 10-minute boiling sterilise, plus 1 minute per extra 1,000 ft
- Using Boiling Water Canners (National Center for Home Food Preservation): Water at least 1 inch (2.5 cm) above the jar tops; vigorous boil; restart timing if the boil stops; lift jars out upright; cool undisturbed 12 to 24 hours
- Cooling Jars and Testing Jar Seals (National Center for Home Food Preservation): Press the middle of the lid; if it springs up it is unsealed; unsealed jars to the fridge
- Storing Home-Canned Jams and Jellies (National Center for Home Food Preservation): Unopened about a year in a cool, dark, dry place; fridge after opening; discard jars with mould, yeast or a fermented, yeasty or alcohol smell
- Bust a glut: how to harvest and store your veg (Garden Organic): Opened jam in the fridge up to 3 months
- Food Safety and Labelling Guidance for small scale home producers (Scottish Borders Council): Three sterilising methods (oven 160°C/gas mark 3 for 10 minutes, hot dishwasher cycle, water above 90°C for 10 minutes); don't reuse lids
- Making Jam and Similar Products (Orkney Islands Council): Same three sterilising methods; don't reuse lids
- Sterilising Jam Jars & Hygiene (Kilner): Advises against oven-sterilising its jars
- Plums: grow your own (RHS): Ripe when soft when gently squeezed; picking over several times as fruit ripens gradually; easily bruised; plums for jams and preserves; first plums to ripen can hold a pinkish caterpillar
- Damsons: grow your own (RHS): Slightly tart raw, rich when cooked, ideal for jams and preserves; picking over several times; easily bruised
- Plum moth (RHS): Pinkish-white caterpillar and light brown excrement pellets near the stone of plums, damsons and gages; affected fruit ripens first; later-ripening fruit much less affected
- Brown rot (RHS): Remove and dispose of brown-rotted fruit promptly to limit carry-over