Storing onions and potatoes so they last months instead of weeks

Both go off for specific, avoidable reasons, and the two of them together is the classic mistake.

Keep them apart. Onions give off moisture and a gas that makes potatoes sprout. Potatoes give off moisture that makes onions rot. Stored in the same bowl, each shortens the other. This single change does more than everything else combined.

Onions

• Cool, dark, dry, and above all ventilated. A mesh bag, a wire basket or a paper bag with holes punched in it.
• Not the fridge, where the cold and damp turns them soft. The exception is a cut onion, which goes in the fridge wrapped.
• Not a sealed plastic bag, which is where the shop's own bag becomes the problem.
• Spring onions and shallots behave differently and keep better cold.

Potatoes

• Cool, dark and slightly humid. Darkness is the important one: light turns them green, and green means bitter.
• Not the fridge. Cold converts starch to sugar, which makes them sweet and makes them go dark when fried.
• A paper or hessian sack, or a cardboard box with the lid loose. Never sealed plastic.
• Sprouts can be rubbed off and the potato is fine. Green patches should be cut away generously, and a very green potato is not worth eating.

Apples nearby will sprout your potatoes, for the same reason apples ripen everything else. Keep the fruit bowl elsewhere.

The realistic version: if your kitchen has no cool dark corner, buy smaller quantities more often. Storage advice assumes a cellar most people do not have.