Potatoes are formed and can be harvested once they start blooming. However you can leave them in the ground a lot longer, until the plants die back, and the potatoes will keep growing. They can be safely left in the ground for up to 6 weeks after the tops have died back as long as the ground doesn’t freeze and you don’t forget where they are. It is best to dig potatoes early in the morning when the ground is cool, and to dig them when the soil is dry. (CCGS Communal Gardeners note: The Peas and Potatoes Team is managing the timing of the potato harvest to maximize the yield so we Communal Gardeners wait for their go-ahead to harvest.)
When you are ready to dig up your potatoes use a pitchfork to loosen the soil about 12-18 inches around the plant (depending on the variety). You can pull the whole plant out and often there will be potatoes attached to it. Then with a hand tool or your hands, dig around in the soil for more potatoes. You want to be careful not to scar the skins with a tool. The plants can go on the compost pile.
With a dry rough cloth (like an old face cloth) or vegetable brush, clean the dirt off your potatoes and inspect them. If the skin is damaged, or there are scabby bumps, set these aside to eat up right away.
The rest of your potatoes, the ones with skins intact, need to be “cured” for about 1-2 weeks to prep for winter storage. Lay them out in a single layer on a screen that is propped so air circulates all the way around, in a cool dark place that is protected from sun, rain and wind. Spread them out on newspaper if you can’t get your hands on a screen. If your Cool Dark Place is also very dry, you can put a bowl of water near or under them to give a bit of humidity. This “curing” helps toughen the skins and heal minor nicks, think the difference between the potatoes you buy in the winter and the ones farmers are selling you right now with the thin flakey skins. Without this step, your potatoes will last 4-6 weeks in the fridge.
To store your potatoes, you can put small batches in boxes or burlap bags and keep them in a cool dark corner of your basement, or alternately if you have limited room, I have had good luck keeping them in a crisper drawer in my fridge through to April. They need a damp, cool spot. High humidity, around 90%, and a temperature of about 4-8 degrees Celsius. At a lower humidity and/or higher temperature, they will go soft more quickly. At a colder temperature the starches start to turn to sugar making them taste odd. This can be fixed by letting them sit at room temperature for a few days before cooking. Freezing will ruin potatoes. They bruise easily so handle with care.
Enjoy your potatoes!