How to Plant Potatoes

Start With Certified Seed Potatoes, Not Grocery Spuds

The single decision that makes or breaks a potato patch happens before you ever pick up a trowel: where you get your seed. I learned this the expensive way, planting a bag of sprouting grocery-store potatoes one March and getting a tangle of weak plants that brought scab into a bed I then fought for two seasons. Grocery potatoes are usually treated with a sprout inhibitor, and even untreated ones can be symptomless carriers of disease.

Buy certified disease-free seed potatoes from a reputable supplier. "Certified" means the stock was inspected and is clean of the viruses and fungal problems that build up in a home patch. I keep a short list of varieties that have earned their place in my clay: 'Yukon Gold' for a dependable all-rounder, 'Kennebec' when I want storage and disease tolerance, and 'Red Pontiac' for a fast red that doesn't sulk in heavy soil.

Chitting and Cutting: Priming the Tubers

Chitting is the gardener's word for pre-sprouting. Two to four weeks before I plan to plant, I lay the seed potatoes eyes-up in an old egg carton or shallow tray and set them somewhere bright, frost-free, and cool, around 50 to 60°F. By planting day each tuber carries stubby green-purple sprouts about half an inch long. Those are exactly what you want; long pale string-sprouts grown in a dark drawer snap off and set the plant back.

Seed potatoes the size of a golf ball go in whole. Anything bigger I cut into chunks, each piece holding one or two eyes and roughly the size of a large ice cube. After cutting I leave the pieces on a tray for a day or two so the wounds callus over — a dry corky skin that shrugs off the soil rots that take freshly-cut flesh. In a cool wet spring, I skip cutting entirely and plant small whole tubers; they're far more forgiving.

• Use a clean, sharp knife and wipe it between potatoes if you suspect any disease.

• Aim for at least one eye per piece; two is insurance.

• Let cut pieces callus 24 to 48 hours before planting; never plant a fresh wet cut into cold soil.

When to Plant by USDA Zone

Potatoes want cool soil but not cold. Seed pieces dropped into soil below 45°F sit dormant and often rot before they sprout; the sweet spot at planting depth is 50 to 60°F. The reliable rule is to plant 2 to 4 weeks before your average last frost, then let the hilled soil protect the emerging shoots from late cold snaps.

I sit in zone 7b on heavy clay, and mid-March is my line. Plant much earlier here and the clay stays cold and sodden, which is exactly what rots a cut tuber. If you garden in the Deep South, treat potatoes as a cool-season crop and aim for a late-winter or even fall planting, since high summer heat shuts tuber formation down.

Depth, Spacing, and the Hilling Method

Dig a trench or individual holes and set each seed piece eyes-up. In cool early-spring soil I plant 3 inches deep; if the soil is already warm and dry I go to 4 inches. Space pieces 10 to 12 inches apart down the row, with rows 30 to 36 inches apart — or 12 inches each way if you're working a raised bed. Crowd them and you trade size for count; every plant ends up fighting for the same handful of nutrients.

Hilling is the part beginners skip, and it's the part that matters. As the plants grow 6 to 8 inches tall, pull loose soil, straw, or compost up around the stems, leaving the top few inches of leaves exposed. Repeat every couple of weeks. Tubers form along the buried stem, so the more stem you bury, the more potatoes you get — and the hilling keeps developing tubers out of the light. A potato shoulder exposed to sun turns green and produces solanine, which is bitter and mildly toxic, so cover anything that surfaces.

Growing, Feeding, and Harvest

Potatoes are organic-first by nature: I work compost and a little aged manure into the bed before planting and rarely reach for anything stronger. They want steady, even moisture once the tubers start sizing — about an inch of water a week — and they hate sitting wet, which is the other reason loose, well-drained, hilled soil pays off in clay country. Mulch with straw between the rows to hold moisture and smother weeds.

Harvest timing follows the variety. Early types are ready 60 to 80 days out, midseason 80 to 100, and late maincrop 100 to 130. For "new" potatoes, wait until the plants flower, then reach gently under the soil and steal a few tubers, replacing the soil so the plant keeps producing. For full-sized storage potatoes, wait until the tops yellow and die back, stop watering for a week or two to firm the skins, then lift the whole plant with a fork on a dry day. Cure them in the dark at cool temperatures for a couple of weeks before storing.

If you're tight on ground or your soil is unworkable, potatoes are one of the easiest crops to grow in a container. I've had clean harvests from fabric grow bags on a gravel pad — same hilling logic, just topping up the bag with soil as the plant climbs.

Frequently Asked Questions