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