How long do fresh berries last in the fridge?

The honest range: blueberries usually hold for one to two weeks, strawberries for three to five days even though the packaging often implies closer to a week, and raspberries or blackberries for as little as two to three days before the first grey-blue fuzz shows up. Berries are not sold half-spoiled, and nobody mishandled them on the way home. A berry's clock starts before it is ever picked, and nothing about how it looks through the clamshell tells you how far along that clock already is.

Why berries mold faster than almost anything else in the kitchen

Most produce arrives with a mostly intact skin standing between it and the mould spores that are everywhere in the air and the soil. A berry does not get that advantage. Mould spores are already on the surface by the time it is picked — they came with the field, the rain, the hands that harvested it — and a berry's own skin is thin, easily broken, and in some cases openly compromised before it even reaches the shop: a strawberry carries a scar exactly where the stem was pulled off, and a raspberry is not solid at all but a cluster of tiny drupelets built around a hollow core, which gives it more surface area relative to its volume than almost any other fruit sold whole. Add to that the fact that berries are picked ripe and do not keep ripening afterward the way a banana or an avocado does — there is no grace period where the fruit is still getting better. From the moment it is picked, the only direction is down. And because a punnet packs dozens of berries touching each other in a small, humid, mostly sealed space, one weeping or bruised berry does not stay a private problem. Mould spreads through contact and through the moisture trapped in the container, so a single bad one can turn an otherwise fine punnet within a day.

Why washing them the moment you get home makes it worse

The instinct to rinse berries before they go in the fridge is reasonable and backwards. Mould spores need moisture to germinate, and a wet berry sitting in a sealed container for days is giving them exactly what they need. The better habit is to store berries dry and rinse only the portion you are about to eat, right before you eat it. If you genuinely want to buy in bulk and stretch the window, a brief dip in diluted vinegar — roughly one part white vinegar to three or four parts water — does kill a meaningful share of the surface spores, and it is a real technique, not folklore. But the part that actually matters is what happens next: drying the berries completely, ideally spread out on a towel rather than piled back into a damp container, before they go anywhere near the fridge. Skipping the vinegar costs you little. Skipping the drying step undoes the whole point of doing it.

What actually decides the window for each kind

Blueberries have a thicker, waxy skin and a low surface area relative to their volume, which is most of why they are the most forgiving berry in the fridge — a week to two weeks is realistic if they go in dry. Strawberries carry that one guaranteed weak point at the stem, softer flesh underneath, and a lot of surface area for their size, so three to five days is closer to the truth than the week the packaging sometimes implies — that number assumes handling most berries never actually get between the field and your fridge. Raspberries and blackberries are the most fragile of the common berries because of the hollow, many-part structure itself, not because of how they were grown or shipped; two to three days is the honest number, which is really a case for buying the amount you will eat this week rather than the amount that was on sale. The container matters almost as much as the berry. The ventilated clamshell they are sold in is designed to let moisture escape, and sealing berries into an airtight container after buying them traps the humidity that mould needs. Lining the container with a paper towel and not overfilling it helps for a simple mechanical reason: berries at the bottom carry the weight of everything stacked on top, and a bruise is a moisture leak — exactly where mould gets its first foothold.

Telling real mould from a berry that is just past its best

Visible fuzz — white, grey, or a blue-green cast on darker berries — means the berry is done, and so is anything it was touching, because what you can see is only the visible edge of a colony that has already been spreading through contact and moist air. A berry that is soft, slightly shrivelled, or weeping juice but shows no fuzz is a different situation: it has simply passed its best for eating raw, and it is genuinely fine cooked into something — a quick compote, a smoothie, folded into muffin or pancake batter — where texture stops mattering and only flavour does. It is worth actually lifting the top layer to check underneath rather than judging the whole punnet by what is on top, because weight and trapped moisture concentrate at the bottom, and that is where mould most often starts before it is visible from above.

What actually makes this easy

• Buy the amount you will use this week, especially raspberries and blackberries. Their window is too short to reward buying ahead.
• Store dry, and wash only what you are about to eat. A wet berry in a sealed container is doing mould's work for it.
• Line the container and do not overfill it. Berries at the bottom should not be carrying the weight — and the bruises — of the ones stacked above.
• Check the bottom layer, not just the top, before deciding a punnet is still good. That is where weight and moisture concentrate, and where mould often starts unseen.

Berries are also the food most likely to disappear behind something bigger and get found a week later, because the quantity is small and the window is short enough that the gap between "just bought" and "already gone" is only a few days — barely enough time to even notice they are there. Munch logs each batch with the day it went in and where it is stored, shared with everyone in the house, so a small punnet of raspberries with three days left surfaces in the same list as everything else, instead of quietly losing to whatever is stacked in front of it.