“Never put your sweet potatoes in the fridge” is neither a proverb nor a euphemism, but simply the most important rule for storing the edible tuberous roots of Ipomoea batatas.

As soon as a sweet potato’s leaves are touched by autumn frost, cut off the foliage and dig up the plant.

The tubers are quite easily snapped or bruised, so handle them gently. Rub the worst of the mud off but don’t wash them, and put them in a warm room to “cure” for a week or so.

By then, any wounds should have calloused over and the tubers should feel dry to the touch — nice and solid, not shrivelled at all.

Now put them in paper bags and keep somewhere cool but not cold. They should last right through the winter like that.

However, some gardeners find this vegetable impossible to store, while others find it easy, and no-one seems to know why.

To avoid the uncertainty, you could just eat them straight away or cook them in dishes for the freezer. But at least try to keep some of the smaller tubers, those that aren’t big enough to be worth eating, to use for propagation.

In March or April plant them horizontally in multipurpose compost in small pots or trays and put them somewhere warm and bright, like a kitchen windowsill or a conservatory. Don’t water them too much or they’ll rot.

After a while — and it can take several weeks — reddish shoots will appear above the compost.

Once a shoot is about three inches long and has about six leaves on it, it’s ready to become a “slip.”

Slice it off and bury it upright, with just the top pair of leaves showing, in a four-inch pot of multipurpose compost.

Any time roots appear through the drainage holes underneath, the new plant needs moving on to a pot one size bigger.

Don’t be in a hurry to put them outside — sweet potatoes won’t tolerate chilly spring nights.

Early June is soon enough to plant them about a foot apart, in a deep hole so that at least half the plant’s initial height is below ground.

My best results have come from growing them in large pots, rather than in the open ground, but wherever you try them, they’ll need lots of watering, and also benefit from regular feeding.

Incidentally, in some countries this crop is grown purely for its leaves, which are used as spinach.

To get started with sweet potatoes, order young plants from a seed catalogue in late winter.

Tubers bought for eating may have been treated to prevent them sprouting, which would render them useless for growing and in any case won’t be from stock bred specifically for British conditions.

Centuries ago, sweet potatoes were called “potatoes,” before the new-fangled “Irish potato” took that name, and can be cooked in all the same ways as spuds, but also used in sweet puddings. They’re nutritious things, being much higher in calories and vitamin C than potatoes are.