British supermarkets have trained us to expect tomatoes, cucumbers and asparagus throughout the year. Their year-round presence can make seasonality seem obsolete.

But the seasons have not disappeared. When British weather cannot provide the light and warmth a crop needs, growers must recreate those conditions or retailers must bring the crop from somewhere that has them.

Both options carry costs, and this winter several of those costs are converging. That does not guarantee a shortage or a particular supermarket price. It does mean that some familiar out-of-season vegetables are unusually exposed to rising production and supply costs.

Tomatoes show the problem particularly clearly. A tomato plant needs sufficient light and warmth to maintain photosynthesis, flowering, fruit development and ripening. In a British winter, a commercial glasshouse may therefore require heating, supplementary lighting, ventilation, humidity control. They also pump in extra carbon dioxide, which can boost photosynthesis and yields. Pumps, fans and irrigation systems also consume energy.

These technologies make winter production possible, but not automatically cheap. The National Farmers’ Union warned in March 2026 that higher electricity network charges could add more than £1 million to the........

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