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Rhubarb Jam
Wash young rhubarb and cut it into pieces about one inch long. Do not peel. Weigh, and to each pound allow three-quarters of a pound of granulated sugar. Put it in a porcelain kettle, bring slowly to boiling point, then boil and stir continually three-quarters of an hour. Put this in jars and hermetically seal, or it will keep in tumblers tied with paper. This makes excellent pies in winter. IO
A two-ingredient preserve that depends entirely on the sugar ratio and on cooking the fruit down far enough to set. Two things in the original need updating: the boiling time and the sealing method.
- Stalks onlyUse only the pink stalks. Rhubarb leaves contain oxalic acid and related compounds in quantities that make them genuinely poisonous; trim and discard them along with any leaf base still attached.
- The sugar ratioThree-quarters of a pound of sugar to each pound of prepared rhubarb, weighed after cutting. That is roughly 1 3/4 cups granulated sugar per pound of fruit. The ratio is what preserves the jam, so do not reduce it if you intend to keep the jars.
- Porcelain kettleThis means an enamelled cast-iron or enamel-lined pot. Rhubarb is strongly acidic and will pick up a metallic taste from bare aluminium or unlined copper. Stainless steel is the modern equivalent.
- Let it stand firstNot in the original, but useful: leave the cut rhubarb and sugar together for an hour before heating. The fruit releases its own juice and the sugar dissolves before the pan goes on, which reduces scorching during the long boil.
- Forty-five minutes is too longYoung rhubarb collapses in ten minutes and the jam may reach setting point well before three-quarters of an hour. Boil hard, stirring, and start testing at the 20-minute mark: 220F on a thermometer, or a spoonful that wrinkles when pushed on a chilled plate. Cooking to the full 45 minutes gives a dark, caramelised jam that is closer to a fruit butter.
- SealingJam covered only with paper, as here, can grow surface mould, which was often simply scraped off. If you want shelf-stable jars, fill sterilised half-pint jars to 1/4 inch of the rim, fit new two-piece lids, and process in a boiling-water bath for 10 minutes. Otherwise refrigerate and use within a month.
- YieldThree pounds of trimmed rhubarb with its sugar gives roughly five half-pint jars, depending on how far it is boiled down.
- The stray "IO"A printer's artifact or contributor's initials carried over from the original page, not part of the method.
Rhubarb reached English and American kitchen gardens as a medicinal plant long before it was eaten, and only became a common dessert fruit in the nineteenth century, once sugar was cheap enough to make its sourness palatable. It comes up in April, weeks ahead of any true fruit, and it was known in American usage as the "pie plant," a name referring straightforwardly to its use in pies. The last line here explains why a cook would boil it in spring at all: sealed in tumblers, it becomes the winter pie filling when nothing fresh is available. Note too that the recipe insists on young stalks and no peeling: early rhubarb is tender enough that the skin softens into the jam and adds to its colour.