Tips on Harvesting and Storing Potatoes

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Potato harvesting generally begins at summer’s end. Photo: http://www.thecapecoop.com

Yes, in the Northern Hemisphere, it’s that time of year again: late summer and early fall is potato harvesting season. True potatoes, that is: Solanum tuberosum. Sweet potatoes (Ipomoea balatas), a very different and unrelated plant, are much slower to mature.

Of course, there are early, mid-season and late varieties of potato, some ready as early as July in some climates, others not until October, but they all show they’re ready to be dug up when their foliage starts to yellow and die back. That can be a scary thing if it’s the first time you’ve grown potatoes—you may think you’re losing your crop!—but that’s how it happens. 

And do note that whether your potatoes bloom or not is not a factor. Some do, some don’t, depending on your climate … but they all produce tubers.

Of course, you can harvest tubers early, while the leaves are still green and healthy. These are “new potatoes”: small and very tasty, but they don’t store well. For potatoes that will last through the winter, wait until the foliage dies back.

A garden fork is a handy tool for harvesting potatoes, but not absolutely necessary. Photo: thecountrybasket.com

Harvest on a dry day, preferably when the soil is quite dry as well. A garden fork is a useful harvesting tool, as you’re less likely to damage tubers than with a shovel. There is even a special flat-tined fork called a potato fork specially designed for potato harvesting. Any tubers you do damage should go straight to the kitchen: they’re not likely to store well. 

Curing Potatoes

Potatoes being cured. Photo: http://www.ourstoneyacres.com

To store well, potatoes need to be cured (hardened off). This treatment helps thicken their skin and, usually, the thicker the skin, the better they store. It also allows minor nicks and scratches to heal over.

With a soft brush or cloth, brush off or wipe off as much soil as you can. Some people like to hose theirs down to remove soil and that’s fine in dry climates, but a bit risky in humid ones, as rot can set it. And, as any gardener will tell you, a little dirt never hurt anyone. Leave any thorough cleaning until just before you cook them.

Now, place the tubers in an aerated box or container or spread them over newspaper and, if they’re in the sun, cover with a cloth (don’t expose tubers to too much light). Place in a cool, dry, well-aerated spot, like a tool shed or garage. Temperatures of 45 and 60˚F (7 and 15˚C) and very high humidity (85 to 95%) are ideal for curing. Ten to 14 days are all that are needed to cure most potatoes.

Storing

Give cured potatoes a once-over, removing bruised, soft or discolored tubers. 

The root cellar is the traditional place to store potato tubers. Photo: foodal.com

If you’re just hoping to keep your potatoes for a month or two, say until Christmas, you can store them pretty much anywhere that isn’t hot and dry. For longer storage, until spring, though, you’ll need distinctly cool, humid conditions. Avoid really cold spots, though, below 40˚F (4˚C), as the tubers tend to sweeten and then won’t fry well, so the fridge is out. Above 60˚F (15˚C), however, they dry out. So you need “cool but not cold.” A root cellar is ideal, but not many people have one any more. You should be able to find a cooler spot in a basement or garage, an unheated entrance, or maybe an attic. 

You can store tubers loose in bins or boxes, but they seem to store longer in perforated plastic bags, probably because they then profit from greater humidity. 

Green potatoes, caused by exposure to sun, are bitter and, in fact, poisonous. Cut off the green part before cooking. Photo: indianapublicmedia.org

And you have to keep tubers in the dark. Potatoes exposed to too much sunlight will turn green and become poisonous (I kid you not!) 

Finally, don’t store them near ripe apples, as the latter give off a toxic gas, ethylene, that stimulates premature sprouting.

Inspection

Sprouting potatoes are still edible, but it’s a sign their storage life is coming to a close. Photo: theconversation.com

Check your potatoes once a month or so. Especially be aware of softening, the first sign of rot, as one rotten potato will quickly spread rot to other potatoes. As winter wears on, some will inevitably start to sprout and then shrinkage occurs. Use these first!

Mostly, though, just enjoy your potatoes. They really aren’t that hard to keep!

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Don’t Wash Onion, Garlic and Potatoes at Harvest

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Cure onions under dry conditions before you store them. Source: http://www.gardeners.com

Cleanliness is next to godliness, we’re often told. But that doesn’t mean you should wash bulbs and tubers at harvest time, not if you want to store them at least.

Dry Bulbs Out, Don’t Moisten Them

You probably know that you should leave onions and garlic out in the sun for a week or two after you dig them (although do move them to a shed or garage to dry if the weather is rainy). This helps “cure” them (allows them to build up a thicker outer skin so they store better). Then brush off any excess soil with a soft brush and move them to their winter quarters (a cool, dry storage area).

20180902B www.allotment-garden.org

These onions aren’t spotless. They don’t need to be clean to store well. Source: www.allotment-garden.org

Do not clean them by washing them in water in an effort to get them squeaky clean. The lingering presence of moisture can lead to rot later on, so you want your bulbs to be as dry as possible. It’s better to have a bit of dirt on a healthy bulb (after all, you’ll be peeling them before you serve, them, right?) than a spotless rotting one!

Oops, it’s too late and you’ve already rinsed them off? Well, put them back out in the sun to dry them thoroughly and keep your fingers crossed. Rot doesn’t always set into washed bulbs, but you have just made it that much more likely.

Potatoes

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Don’t worry about a bit of dirt on potatoes when you put them into storage. You can rinse them later, as you prepare them for supper. Source: www.garden.eco

The same applies to potatoes, with the exception that I suggest always curing them indoors (on the floor of a garage or tool shed) in the dark rather than outdoors in the sun, as potato tubers exposed to sun begin to turn green and green potato parts are poisonous. But if you’re worried about dirt, you can carefully brush off any clinging soil rather than washing them. And if they aren’t perfectly clean, don’t worry about it.

Potato tubers too like to be thoroughly dry on the outside before storage, but keep best under more humid conditions that onions and garlic, in a root cellar, for example, where it’s both cool and humid.