Should I start potatoes in cold water or boiling water?
Cold, for anything cut larger than a chunk of a couple of centimetres — and the reason is a heat gradient, not tradition. When a hot start is genuinely fine.
- Difficulty
- beginner
- Time
- 5 min
- Read
- 2 min
Short answer
Start in cold water and bring it up together. A potato conducts heat slowly, so dropping a large piece into boiling water holds its outer centimetre at boiling point for the entire time the centre takes to reach it, and that outer layer disintegrates. A hot start is fine only for small pieces — dice under about 2 cm, or thin slices — where the centre catches up quickly.
This is the one piece of received kitchen wisdom in the potato section that is straightforwardly correct, and it is worth knowing why rather than following it blindly, because the reason tells you when to ignore it.
Step by step
- Put the potatoes in the pan first, then add cold water.Cover by about 2–3 cm. Adding water to the potatoes rather than potatoes to hot water is the whole of the technique.
- Salt now, not later.Roughly 10 g per litre. Salt has the whole heating period to penetrate, which is why cold-started potatoes taste seasoned through rather than salty on the outside.
- Bring to the boil, then immediately drop to a simmer.The gradient argument applies twice. Once the water is boiling you want the gentlest heat that keeps the potatoes cooking, so the outside is not held hard at 100°C longer than it must be.
- Time from the boil, not from switching the hob on.Chunks for mash: roughly 15–20 minutes from the boil. Whole new potatoes: 12–18 depending on size. Whole medium potatoes for a salad: 20–30. Always test rather than trust the clock.
- Use a hot start deliberately where it helps.Small dice for a hash, thin slices for a gratin that will finish in the oven, or potatoes going straight into a soup all cook through fast enough that a boiling start does no harm and saves several minutes. Green vegetables are the opposite case entirely — those go into water already boiling.
Tips
- A lid on until it reaches the boil saves real energy and time; after that a lid makes the simmer harder to control, so take it off or set it ajar.
- The same gradient logic explains why par-boiled roast potatoes work: you are deliberately overcooking the outer few millimetres so it roughs up into a crisp surface.
- Sweet potatoes are not potatoes for this purpose — they are better roasted or steamed than boiled at all, because boiling dilutes their flavour.
Common mistakes
- Waiting for the water to boil before adding the potatoes — It wastes the time you spent waiting and gives you a broken outer layer at the same time.
- Keeping a rolling boil for the whole cook — The water is not hotter than a simmer. All the extra energy goes into agitation, evaporation and your bill.
Questions people ask
Does a cold start apply to all root vegetables?
Broadly yes for dense roots cooked in large pieces — celeriac, swede, parsnip, beetroot. It matters much less for anything cut small, and not at all for green vegetables, which want the shortest possible time in the hottest possible water.
Is it true that potatoes grown underground start cold and things grown above start hot?
It is a memorable rule of thumb and it happens to give the right answer most of the time, but the actual reason is piece size and heat conduction, not where the plant grew.