Potatoes

Grow potatoes from whole potatoes, small potatoes, or a cut piece of a larger potato. Potatoes grow from the dormant buds–called “eyes”–on the surface of other potatoes.

When the buds sprout, they develop into new plants. About two weeks after sprouting, the main stem and first leaves of the new potato plant will appear above ground.

Potato growing
Sprouted seed potatoes are laid out in a row in the garden in early spring.

Preparing to Plant Potatoes

  • Soil. Potatoes grow best in loamy, airy, well-drained soil. Heavy clay soils and soggy soils are the least hospitable to potatoes. To prepare your potato bed, add plenty of aged compost and organic matter–leaves and grass clippings. Potatoes like highly acid soil–a pH of below 5.5 is optimal. (Acid soil discourages scab, a disease that causes the potato’s skin to pit.) If your potato patch has never grown potatoes before, a cover crop of quick-growing annual ryegrass can be planted the season before. Turn the ryegrass under at frost time–this is a “green manure” perfect for preparing your planting bed.
  • Temperature. Potatoes can go into the ground as soon as the soil temperature is at least 40°F, usually two to four weeks before the last expected frost. Potatoes very nearly stop growing when the daytime temperatures rise to greater than 80°F. In very warm summer regions, the potato harvest should be in before the hot weather arrives. In hot summer regions, plant potatoes in early autumn for harvest in mid-winter. Choose potato varieties with harvest times suited to your climate: early-, mid-, or late-season potatoes.
  • Seed potatoes. Plant certified disease-free seed potatoes. Small seed potatoes can be planted whole. Larger potatoes should be cut into pieces that have three or four “eyes”–recessed dormant buds–apiece. Cut the pieces into blocks about the size of a large ice cube. Larger seed pieces produce plants that will yield a large number of medium to small size potatoes. Smaller seed pieces will produce fewer, but larger potatoes. (Each piece contains starch which will nourish the developing new plant.) Cure cut pieces by spreading them out in a warm, bright, airy place for a day or two, or until they are slightly dry and the cut areas have hardened or healed over. (If the soil is warm, you do not need to cure the seed pieces, you can plant them right away.)
  • Sulfur powder. Some gardeners sprinkle sulfur powder on the seed pieces to prevent the pieces from rotting in the ground. This is particularly helpful in wet climates or where the garden stays damp. Sulfur powder can be purchased at the garden center or a drugstore.
  • Sprouting early potatoes. To harvest potatoes early you can force the eyes to sprout before planting the seed potatoes in the garden. To sprout seed potatoes before planting, spread them out in a single layer in a bright, airy place where the temperature will remain about 60°F or warmer. The potatoes will develop short, green sprouts–thus this process is called “greening.” When planting time comes carefully cut the potatoes into seed pieces without breaking the new sprouts.

Ways to Plant Potatoes

  • Trench planting: Plant seed potatoes in 4 to 6 inch-deep furrows. Space furrows or trenches (rows) about 36 inches apart. Sow the seed potatoes cut side down every 10 to 12 inches; don’t plant seed potatoes too close or the yield will drop. Between each seed potato put a half-handful of aged compost or 5-10-10 fertilizer–such as bulb food–into the trench. Cover the seed potatoes with 3 to 4 inches of soil and continue to keep the tubers covered as they grow.
  • Surface planting: turn or till the soil and sprinkle on compost or 5-10-10 fertilizer; rake the bed level. Plant seed potatoes about 10 inches apart in all directions; set the cut side of the seed potato on the planting bed and push it down until the top is even with the ground level. Cover the planting bed with 18 inches of mulch–straw, hay, leaves. The potatoes will grow under the mulch.
  • Container growing: Line a bushel basket, large bucket, half wine or whiskey barrel, or garbage can (a container at least 18 inches deep) with plastic, punch holes in the bottom, and place a layer of stones or gravel at the bottom for drainage. Add 4 to 6 inches of potting mix to the bottom of the container and set the seed potatoes six to eight inches apart. Add another 2 to 4 inches of soil over the seed potatoes. As the plants grow add potting mix, straw, or compost–keep the plants covered except for the top leaves.

Caring for Potatoes

  • Hilling Potatoes. Keep the developing tubers covered. New potato tubers form above the buried seed piece or seed potato. To give the new potato tubers room to expand and grow, the soil should be mounded up around the stems of growing potato plants. This process is called “hilling.” Hilling should happen once or twice during the growing season. Use a hoe to draw the soil up around the stem of the growing potato plant–leave just the top leaves exposed. Hilling keeps the shoulders of new potatoes from poking up through the soil. The skins of exposed potato tubers turn green (called “greening”); green potatoes contain a bitter-tasting, slightly toxic substance called solanine. Hilling also keeps weeds from growing up around potatoes and it ensures that water does not sit on top of growing potatoes, but runs off the hills. Once the potato plants flower, stop hilling up the soil. Apply thick mulch to save water and fight weeds.
  • Watering Potatoes. Keep the potato patch evenly moist but not soggy. Take special care to keep plants well-watered from six to ten weeks after planting as tubers are starting to develop. While potatoes demand well-drained soil, the development of the tuber is dependent on even watering throughout the season. Deep watering is the best practice; the soil should be moist eight to ten inches below the surface. Uneven watering will cause potato tubers to form knobby growths or crack. If the soil is dry, there will be little if any tuber growth.

Harvesting Potatoes

  • Harvesting Potatoes. When flowers open, harvest “new” potatoes. Use your hands to pull aside the hilled-up earth around the base of the plants and gently pluck out the new small, round, smooth tubers. Once the top foliage starts to wither and die back potato tubers are full-grown. Mature tubers can be lifted with a multi-pronged garden fork. If the weather is not too warm or wet, full-grown tubers will keep in the ground for several weeks. But, be sure to get your crop up before the first frost. Don’t let freshly dug potatoes sit in the sun for too long–not more than an hour or two. A cloudy day after a period of little or no rain is ideal for potato harvesting. Nicked or bruised potatoes won’t store well, so eat them first.

Storing Potatoes

  • Storing Potatoes. After freshly dug potatoes have set and dried for an hour, dust away any soil left on them and put them into a dark place for storage. Keep them at temperatures around 55° to 60°F. Let them cure for two weeks; this will allow cuts and bruises to heal. Once cured store potatoes at 35° to 40°F in a well-ventilated basement or root cellar. If the storage temperatures are higher, the tubers may sprout and shrivel. Store potatoes where they get plenty of air circulation. Don’t pile them higher than six to eight inches. Remember not to expose stored potatoes to light; the skin will start to green.

More growing tips at How to Grow Potatoes.

Grow 80 vegetables: The Kitchen Garden Grower’s Guide

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. Harvesttotable.com has more than 10 million visitors each year.

Comments

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  1. Hello, I ended up planting my potatoes late this year. They are in black plastic pots. The foliage is beautiful and some of the first flower buds are starting in August in Zone 5b/6a. Daytime temps ~80, night ~60. I know it’s too warm but I’d like to get some harvest from them if I can. My garden has areas of full sun, morning sun, afternoon sun and the shaded north side of the house w/a little evening sun. I’m also not opposed to covering the pots with light-colored or reflective material if that would help. What would be my best option for positioning the pots? I’m trying to balance sun for the tops while keeping the roots as cool as possible. Any advice would be appreciated.

    • Black plastic pots will collect solar heat and so heat the soil around the tubers. As you suggest placing reflective material such as aluminum foil around the pots would be one way to slow the collection of heat by the black plastic. You could also set your pots inside larger pots so that the larger pots collect most of the heat–and tuck in a layer of insulating straw between the two pots. You can move the pots to a position where the foliage will get morning sun until just before noon but where the pots (and probably the foliage) will not get direct afternoon sun.

  2. Great resource, thanks! I’m just a bit confused about the difference between seed potatoes and taking a mature potato and cutting it into individual “seeds.” In one of your articles, you said if you use the latter method, each piece should have 3-4 eyes. Does each eye produce just one separate potato plant, with its own large, single tuber? Or can you get multiple potatoes from one eye? And, if you just stick whole seed potatoes in the ground, say for example with 4 eyes each, do you then get 4 new plants with one tuber beneath each? I guess my real question is what the heck is happening underneath the ground? I’m trying to do the math and estimate how many mature potatoes we’ll need for the winter & early spring, before the next crop is harvested. I hope to grow them year-round here on the Northern California coast. Maybe even sell them at the farmers market. We rarely get frost or freezes, and when we do I just cover my containers with newspaper. Thanks!

    • Cut pieces of a potato tuber with multiple eyes will produce one plant. The multiple eyes simply ensure that one or more of the eyes will sprout new green growth that is a growing stem. While you could attempt to separate the sprouts growing from one cut piece or from one whole seed potato to create several new plants, that is not an optimal choice; the seed potato or part of seed potato contains stored nutrients the new sprouts need to grow and set roots. The seed potato or piece of seed potato beneath the soil is producing new roots from stored nutrients.

  3. I once observed a farmer treating his seed potato with two chemicals prior to planting. What could those chemicals be? Fungicides, insecticides, nematicides or what could they be?

    • Horticultural sulfur is a powder commonly used directly on cut potato pieces (seed potatoes) to protect them from rot and other soilborne diseases. Sulfur is often used when the soil temperature is below 40F at planting time. Dip each piece in a container of sulfur powder to cover all the cuts in the seed potato. Dipping potato pieces in sulfur helps create a kind of acidic shield around the piece to protect it from developing scab, a fungal disease.

  4. We planted our potatoes around the middle of May and we’ve had a few potatoes that didn’t grow above the ground but we have found some new potatoes in the ground, why does that happen? We live in Saskatchewan Canada zone 2b, so far it has been fairly wet growing season.

    • Potato tubers develop on stolons growing from the lower stem of the plant–not the plant’s roots. Because the potato tubers develop from stolons on the lower stem, you “hill up” or cover the tubers because they are developing above the roots and native soil level. (Hilling up keeps the tubers from the sun and “greening”–turning green from sun exposure–a poisonous alkaloid makes green potatoes taste bitter and they should not be consumed. To avoid greening, keep the tubers covered with well-draining soil or compost or straw or hay (tubers exposed to excessive moisture or irrigation will rot). Stolons generally grow on top of the soil or slightly below the soil level; that explains why you found some tubers in the soil.

      • This is not what I asked, I was asking why we’ve had a few potatoes that didn’t grow above the ground but we have found some new potatoes in the ground, there has been nothing growing above the ground.

    • Potatoes are shallow rooted; they will need lots of water once leaves are fully developed and as tubers enlarge. There is no reason an aqua globe could not do the trick–it should keep your soil just moist. Once the foliage starts to turn yellow, cut back on the water–let the soil dry between waterings–otherwise the tubers will rot.

  5. Hi, I have been trying with some luck to grow garden beds full of things I have grown for years in Idaho. I now live in Las Vegas and would love some tips on how to grow many things. I am looking through everything I can find in the Harvest to Table site and I have printed out many things. I find that I can plant a garden in February here, and that is what I am doing this year. I hope to have gotten a good start on most of my gardening by the time it gets so hot here.

    I would like to know about strawberry plants. I have had some beautiful plants that gave me the best tasting ever berries but when it got hot here they dried up and turned to mulch. Can you tell me how to have a good berry bed that will not dry up?

    • There are several articles on hot weather gardening here at Harvest to Table, find them listed in the Topics Index under Hot Weather Gardening. The key to vegetable gardening where summers are hot is to do your gardening in the cool and warm times of the year and let the garden rest during the hot summers. Success comes down to timing; schedule your planting and harvest so that you the garden can take a break once temperatures are consistently hotter than 85F.

      For strawberry growing in hot summer regions, to to the Topic Index and look under Strawberries for the article: Growing Strawberries in Hot Summer Climates.

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