UK gardeners can make jam from six common garden fruits: strawberry, raspberry, blackberry, plum, gooseberry, and blackcurrant. The setting point is 104.5C, tested with a sugar thermometer or the wrinkle test on a cold saucer. The standard ratio is 1kg fruit to 1kg granulated sugar. High-pectin fruits like blackcurrants and gooseberries set easily, while strawberries need added lemon juice. Properly sealed jam stores for 12 months.
Key takeaways
- The jam setting point is exactly 104.5C, measured with a sugar thermometer
- Standard jam ratio is 1kg fruit to 1kg granulated sugar for most recipes
- High-pectin fruits like blackcurrants and gooseberries set most easily without additives
- Strawberry jam needs the juice of 2 lemons per kg of fruit to reach a firm set
- Properly sterilised and sealed jam keeps for 12 months in a cool, dark cupboard
- A 3kg batch of fruit makes roughly 10-12 standard 340g jars of jam
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Our team produces practical UK gardening guidance from source research, contributor records and established horticultural practice. Editorial standards are overseen by Matt W.
