Storing potatoes and onions properly
Dark, cool, airy — and never together. Potatoes next to onions sprout twice as fast.
Potatoes want it dark (light turns them green and bitter — the solanine is inedible), cool between 4 and 10 °C (in the fridge the starch turns to sugar and they taste sweet) and airy (in a plastic bag they sweat and rot). A jute or paper bag in the cellar, the pantry or the lowest kitchen cupboard is ideal.
Onions and garlic want the same — just not in the same place. Onions give off ethylene, which makes potatoes sprout, and the moisture of potatoes makes onions mould. Two corners, two bags.
An apple in the potato sack is the old anti-sprouting trick: apples also give off ethylene, but in a dose that inhibits sprouting rather than promoting it. It genuinely works.