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Lemons
Buy lemons in February or March when they are the lowest in price and can in cold water in the same manner as rhubarb.
This one-line entry belongs to the old "cold water canning" tradition, in which fruit was packed raw into jars, covered with plain cold water, sealed, and set aside with no heat processing at all. The method is no longer considered sound, and the notes below explain what the instruction assumes and where it fails.
- What "can in cold water" meantThe reader is referred back to the rhubarb entry, which is not reproduced here; cold water canning generally meant packing raw fruit into clean jars, covering with cold water, and sealing. This entry itself specifies no boiling, no processing time and no temperature.
- No heat step means no kill stepNothing in the jar ever reaches a temperature that destroys mould, yeast or bacterial spores. The method relies entirely on the acidity of the fruit and the exclusion of air, both of which are undermined here.
- The water dilutes the acidLemon flesh is strongly acidic, but peel and pith are much less so, and filling the jar with plain water lowers the acidity of the contents as a whole. Because no acidity is measured here, there is no assurance that the whole jar stays below the pH 4.6 threshold relied on to prevent growth of Clostridium botulinum in a sealed, airless container.
- Whole lemons carry surface contaminationCitrus rind is waxy, porous and routinely carries mould spores and soil organisms. Unheated, unacidified, and shut away from air, those organisms have weeks or months in which to work.
- The rhubarb method itself is obsoleteCold water canning of rhubarb appears in household books of this period and is not endorsed by current food safety guidance. A recipe that says "do it the way you did the rhubarb" inherits all of that method's problems.
- No quantities, no yield, no seal checkThere is no jar size, no fruit quantity, no headspace, no sealing instruction and no way to verify that a vacuum ever formed. Even setting the microbiology aside, there is not enough information here to reproduce the procedure.
- If you want preserved lemonsUse a current, tested recipe — salt-preserved lemons, marmalade, or a properly processed lemon curd or syrup all have modern formulations with measured acid, salt or heat treatment.
Early twentieth-century preserving manuals were written for households that bought produce by the crate when it was cheap and had to make it last, and the advice to buy lemons in February or March reflects a seasonal low in the price of citrus. "Cold water canning" enjoyed real popularity in this era; it cost no fuel and no time, and its apparent successes owed a good deal to high-acid fruit, cool cellars and short storage, while its failures went largely unrecorded. The compression of the entry to a single sentence is itself characteristic of the genre. Systematic processing times and temperatures for home canning were not established until later, through agricultural extension work, and that research is generally credited with pushing the cold water method out of use.