ONE of the most annoying gardening myths is that potatoes will flower when they’re ready to harvest.

It’s annoying because it’s partly true — there are some varieties, mostly earlies and second earlies, which will give you this helpful signal. But there are many more that don’t, and if you wait to see flowers before you start digging, you’ll still be waiting long after the plants have been destroyed by frost.

It’s convenient to divide spuds into two categories: those for eating fresh, and those for storing. First earlies, usually harvested in early to mid-summer, are always eaten fresh because they don’t store well. Second earlies can be used either way: that is, dug up when needed for boiling, or left to mature. Maincrop potatoes are grown primarily for keeping.

The only foolproof way to tell whether early varieties are ready is to feel around in the soil beneath the foliage with your fingers. Do it gently, so as to cause as little disturbance as possible. The rule here is quite simple, though rather subjective: if the tubers have reached a size at which you fancy eating them, then eat them. If not, try again next week.

Maincrop tatties are available for harvesting in late summer or early autumn. The exact date will depend on various factors, such as the variety you’ve planted, when you planted them and what sort of weather you’ve had.

At some point during this period the leaves and stems of the plants, known as “haulms,” will start to die back. They turn yellow and begin to shrivel, often leading to panic among new gardeners who think they’re being attacked by disease. Once the haulms reach this stage, I like to cut them off with secateurs — some authorities believe this helps the tubers ripen.

Next, leave the plants alone for about 10 days to a fortnight, which gives the potatoes a chance to develop skins. Without its “jacket” a spud will dry out excessively, become rubbery in texture and won’t store properly.

Now, at last, you can dig them up. Choose a dry day if possible. Go carefully: you’ll almost inevitably spear a few of the precious tubers with your garden fork, but if you start work a fair way out from the centre of the plant, you’ll minimise losses.

Dig up one plant first, and let the potatoes sit in the sun for an hour or so until their skins feel dry to the touch. Then check that the skin really has set by giving it a rub with your thumb. If the skin slides off, then leave the rest of the crop for another week.

Such thin-skinned spuds, and any with visible damage, should be set aside for immediate use as they won’t keep. Put the rest, after drying in the sun, in light-proof sacks or paper bags, somewhere cool but frost-free. Check regularly for any that have gone off, and the bulk should last for months.