Every September the same scene plays out on balconies and allotments: plants that were unstoppable in August now looking bedraggled, leaves going spotty, and clusters of tomatoes sitting there stubbornly green while the evenings get shorter and cooler. The temptation is to leave them out and hope for one last warm week. Usually what arrives instead is a cold snap, and cold-shocked tomatoes go mealy and sulk rather than ripen.
The good news is that tomatoes do not need the plant to ripen. They need warmth and ethylene, the gas that fruit produces as it matures, and both of those are easier to supply in your kitchen in October than they are outdoors.
Pick at the right moment, not the last possible one
The fruit worth saving is the one that has reached full size and has started to shift from hard grass-green towards a paler, slightly glossy green, sometimes with a faint blush at the blossom end. That change means the seeds have matured and the fruit has what it needs to finish. Small, dull, rock-hard tomatoes the size of a marble will not ripen no matter what you do with them — those are for the compost or for cooking as green tomatoes.
Pick before the first properly cold night rather than after. Leave a little stalk on each fruit, handle them gently, and pass on anything with a split, a soft patch or a bit of mould, because one going over will take the whole tray with it. Give each one a wipe with a dry cloth rather than a wash; damp skin invites rot.
