There is quite a bit of discussion surrounding the handling of seed potatoes. Oftentimes, you’ll receive both large and small tubers in your seed potato order, and people wonder about cutting up the larger pieces in order to get more use out of them.
The general rule is that the pieces you plant should each have about 2 eyes (sprouts) somewhere on their skin. If your potatoes have arrived with no eyes or sprouts on them, you’ll need to “chit” them before cutting them. Chitting potatoes is a method of preparing the potatoes for planting by laying them in a single layer in a room that is around 60°-70° F with access to light. The light will allow the sprouts to grow stocky and green. After about 4-6 weeks, you should see short but strong green & pink shoots. You do not want the long, spindly, white ones that you may see coming off a potato that has simply sat around too long without being used.
Some gardeners debate over whether cutting the larger pieces into small pieces makes them vulnerable to all kinds of pests and disease once they’re placed in the ground. However, some say that allowing the cut potatoes to “heal over” or form a scab over the exposed meat will prevent any pest or disease issues. It is suggested to allow the cut potatoes to cure in a humid environment for a least 2-3 days, which will also help them retain moisture. There are others (including a reference from the USDA), who insist that planting the potatoes immediately after cutting them is the way to go. The argument is that the viability of the cut potato is lowered by the loss of moisture while it cures. This theory may be applicable when the soil you are planting into is warm (late spring). However, if you’re planting into cool, moist soil (early spring), you are inviting rot organisms to devour the pieces.
There are alternative methods to protecting the cut potatoes than allowing them to cure. You can use sulphur powder, which is available at most drugstores. Simply drop the cut potatoes into a paper bag with a few tablespoons of sulphur powder and shake to coat. The powder sticks to the cut pieces and protects them from rot and pests.
Keep in mind that you should always buy your seed potato from a certified seed potato source. Using store bought potatoes is not suggested, as they are typically treated with a substance that prevents them from sprouting.
Once you’re ready to plant, be sure to be aware of your area’s last spring frost date. In general, seed potatoes should be planted about 2-3 weeks before the last frost date. Keep an eye on the weather and temperature during the summer. If the temperature climbs up beyond 90°F, the potato plants are likely to keel over and die. If you tend to have hot summers, start the potato process earlier to accommodate.