Why grandparents kept carrots in a box of sand all winter, and why experts still recommend it

I remember seeing a box of sand in my grandparents' shed years ago and wondering why on earth they kept it there.

At the time, I didn't think much of it. It was just one of those slightly odd things you come across in an old garden shed and never really question.

But with winter just around the corner, it feels like a good time to bring this one back. What looks like an ordinary box of sand can actually be surprisingly useful when you're trying to get through the colder months.

It might sound strange at first, but there's a clever little trick behind it — and it's one that gardeners have been using for generations.

So, what is the sand actually for?

The Royal Horticultural Society's guide to storing root vegetables still recommends the method for several crops, including carrots, beetroot, celeriac and swedes.

The idea is to place the vegetables in layers of moist sand inside a box, then keep them somewhere dark and frost-free, such as a shed or cellar. The sand helps prevent vegetables that are prone to losing moisture from shrivelling during storage.

The method isn't limited to those four vegetables, either. The RHS also lists parsnips, salsify, scorzonera, turnips and winter radishes as suitable for winter storage.

How to make your own sand box

Start with vegetables that are in good condition. Damaged or bruised roots are more likely to deteriorate in storage, so the Farmers' Almanac's guide to sand storage recommends selecting mature, unblemished vegetables and leaving damaged ones out.

Remove the leafy tops and brush off loose soil. Don't wash the vegetables before storing them.

Then choose a clean wooden crate or plastic container. Add a layer of slightly damp sand to the bottom and place the vegetables on top, leaving a little space between them.

Cover them completely with another layer of sand, then add another layer of vegetables. Continue until the container is full, making sure the final layer is covered with sand.

The sand should be slightly moist, not wet. Iowa State University Extension recommends cool, humid conditions for carrots, while its specific advice on storing carrots says large quantities can be buried in sand or sawdust and kept just above freezing.

A cool garage, basement, cellar or unheated storage room can work, as long as it stays above freezing.

Don't just pack it away and forget about it

Even under good conditions, stored vegetables need an occasional check.

The Farmers' Almanac recommends checking stored vegetables regularly and removing anything that develops soft spots or signs of deterioration. The RHS also warns that storage rots can affect roots kept in unsuitable conditions.

Rodents can be another problem, particularly if the box is kept in a shed or garage. The RHS specifically notes that rats, mice and voles may need to be controlled around stored root crops.

There's also another reason not to put everything in the same box. Farmers' Almanac advises keeping apples away from root vegetables because apples release ethylene gas, which can speed up ripening and deterioration.

You don't always need a box

There's another traditional way to keep some root vegetables through winter: leave them in the ground.

The RHS says carrots can be left in the soil until needed. Covering the ground with a 15cm layer of straw, cardboard or bracken, held down with netting or horticultural fleece, can protect them from the cold. They can keep until March if necessary, although indoor storage is needed in colder regions.

Beetroot can also be left outside, but it needs more protection. The RHS recommends a 30cm layer of straw, cardboard or bracken to protect the roots from hard frost.

For gardeners who have already harvested their crop, though, the humble box of sand offers another option.

It's simple, inexpensive and doesn't require any specialist equipment. Just a suitable container, some slightly damp sand and somewhere cool and frost-free to keep it.

And that strange box sitting in an old garden shed suddenly makes a lot more sense.