How to Cut Seed Potatoes
Potatoes (Solanum tuberosum) aren’t typically cultivated from the seeds in the tiny fruit their blossoms sometimes produce. Instead, preparing potatoes for planting means taking some of the tubers from last year’s crop and leaving them to create new sprouts. Once sprouting begins, the potatoes are usually – but not always – cut up before planting.
Seed Potatoes vs. Supermarket Potatoes
Some gardeners routinely use potatoes from the supermarket as their seed, while extension services from the University of Minnesota and other schools typically recommend buying seed potatoes from a reputable supplier instead. So, what’s the difference between seed potatoes and regular potatoes?
For one thing, supermarket potatoes are often treated to inhibit sprouting. That’s good for the grocer, but bad for the gardener. You also don’t get much choice about which cultivar you grow. Supermarket potatoes varieties grow well in Idaho, Maine and the other primary potato-growing areas. If you don’t know where they originated, you won’t know if they’re suitable for your local microclimate.
The biggest reason to buy your seed potatoes from a reputable grower is to avoid disease. Certified seed potatoes are known to be disease-free, so you won’t waste your whole growing season on potatoes that will be blighted. Even worse, once you’ve introduced a pest or disease to your garden, it might be years before you can grow potatoes successfully again. It’s a risk that’s hard to justify.
Cut Seed Potatoes or Not
You can plant a whole seed potato for each space in your garden, but you don’t need to. Depending on their size, you might easily get two to four viable pieces from each seed potato you buy. That’s a pretty effective way to maximize your purchase, though it’s not an option for fingerlings or smaller seed potatoes of 1 1/4 to 1 1/2 inches.
Some gardeners argue that they get higher yields per plant by planting the whole seed potato. Others feel they get a bigger overall harvest from cutting up their seed potatoes, creating more individual plants. Feel free to experiment by planting both ways and evaluating which option works best in your soil with the cultivars you’ve chosen to grow.
Preparing Potatoes for Planting
If you settle on cutting your seed potatoes, start by checking each potato for “eyes” or buds, which will become new sprouts. Each piece you cut must contain at least one eye, and having two to three is better. Each piece should be about 1 1/2 to 2 ounces in weight. If you’d like a visual guide to the correct method and size, Iowa State University’s extension service has a useful video on its potato-planting page.
Once the potatoes are cut, set them aside in a warm, well-ventilated area for at least two to three days and, preferably, four to five. This gives the cut surfaces time to scab over and dry, which protects them from rotting once they’re in the ground.
Planting Your Potatoes
Potatoes are heavy feeders, so prepare the soil either in autumn or early spring with manure and compost. Choose a spot with well-drained, sandy soil if possible.
Potatoes can be planted a few weeks before the last frost, as soon as the soil is dry enough to be workable. There’s often an element of tradition involved: Midwest gardeners might aim to plant by Good Friday, while the University of Florida cites Valentine’s Day. Whatever your location, the soil should be dry enough to till and at a temperature of around 50 degrees Fahrenheit, so the seed potatoes won’t rot.
Plant the seed potatoes cut-side down and 3 to 5 inches deep, because they’ll push up as they grow. Plants should be 10 to 12 inches apart and in rows about 30 inches apart. Potatoes in tight quarters yield more, but they’re smaller spuds. Those with more elbow room provide fewer, yet larger, potatoes.
Growing and Harvesting Your Potatoes
Once your potatoes have reached about a foot in height, gather a few inches of soil around the stems to create a small hill. Do this another time or two during the season, until 8 inches or so of soil is mounded up around them. The covered areas of stem will produce additional tubers to maximize your yield. It also covers the potatoes as the growing tubers push to the surface. This is important: Potatoes exposed to the sun become green and develop toxic, bitter-tasting alkaloids.
You can begin harvesting your potatoes as “new” or “baby” potatoes by mid-season, running your fingers through the soil to extract a baby spud or two from each plant. Your main harvest comes when the plants’ tops have died back and the tubers have reached their mature size. A couple of weeks in the ground after the plants shrivel toughens the potatoes’ skins, and it improves their storage life. However, you need to dig them up before the ground freezes.
Leave the potatoes to dry in a well-ventilated area for a week or two; then brush off any loose soil and store them in a dark, cool place for the winter. Any that are damaged or beginning to shrivel should be eaten first, as they won’t store well.
- Only plant certified disease-free seed potatoes to further prevent disease and rot problems.
- Small seed potatoes that only contain one or two eyes do not require cutting. For example, most fingerling potato varieties are planted whole.
Fred Decker is a trained chef and prolific freelance writer. He was educated at Memorial University of Newfoundland and the Northern Alberta Institute of Technology. His articles have appeared on numerous home and garden sites including Our Everyday Life, GoneOutdoors, TheNest and eHow.