Planting and Growing Potato

The potato (Solanum tuberosum) is a member of the nightshade family, which includes tomato, pepper, and eggplant. This cool-weather vegetable typically yields bigger crops in the northern portion of the U.S., however, they can be grown as a winter crop in warmer climates.
The edible part of the potato is the underground “tuber” which is an enlarged underground storage portion of the potato plant. The tuber develops from underground stems called stolons once the plants are 6 to 8 inches tall, or around 5 to 7 weeks after planting.

PLANTING

Plant potatoes in a sunny place with at least 6 hours of directly sunlight each day. The tubers need to grow in fertile, loose, well-drained soil; hard or compacted soil leads to misshapen tubers. Ideally, soil is slightly acid (pH 5.8 to 6.5) and the soil temperature is at least 45º to 55ºF  (7° to 13°C). Before planting (preferably in the fall), mix compost or organic matter into the soil. 

When to Plant Potatoes

Garden potatoes can be planted as soon as the soil can be worked. For many gardeners, this is about 2 weeks after the last spring frost. But aware that early crops may be ruined by soil that’s too wet as the potato seeds will rot. Pay more attention to the soil than the calendar to determine planting time. The soil should not be so wet that it sticks together and is hard to work. Let it dry out a bit first. If you have a late and wet spring, you can plant later—through April (depending on location) or even June, especially in containers. 

In cooler regions, some gardeners will plant the first crop of “early-maturing” potatoes in early to mid-April, 6 to 8 weeks before the average last frost date. These varieties can withstand frost.

In warmer regions, potatoes can be grown as a winter crop and planting times range from September to February. Where winters are relatively mild, you can plant a fall crop in September. For example, in central Florida, gardeners plant potatoes in January, and in Georgia they plant in February.

How to Plant Potatoes

Note: Potatoes are usually planted in the ground, but they also can be grown in large containers or baskets. The same planting information applies.

Use certified (disease-resistant) seed potatoes from which eyes (buds) protrude. (Do not confuse seed potatoes with potato seeds or grocery produce.

• One to 2 days ahead of planting, use a clean, sharp paring knife to cut large potatoes into golf ball-size pieces, with 1 to 2 eyes each. This time allows the pieces to heal, or form a protective layer over the cut surface, improving both moisture retention and rot resistance. Do not cut up seed potatoes that are smaller than a hen’s egg; plant them whole. 
• Potatoes grow best in rows about 3 feet apart. With a hoe or round-point shovel, dig a trench row about 6 inches wide and 8 inches deep. Taper the bottom to about 3 inches wide. Spread and mix in aged manure, compost, and/or leaves.
• In each trench, place a seed potato piece cut side down every 12 to 14 inches and cover with 3 to 4 inches of soil.

Growing

• Maintain even moisture, especially from the time after the flowers bloom. Potatoes need 1 to 2 inches of water a week. Too much water right after planting and not enough as the potatoes begin to form can cause them to become misshapen. Stop watering when the foliage begins to turn yellow and die off.

Hilling keeps potatoes from getting sunburned, which can cause them to turn green and produce a bitter, toxic chemical.

Hilling Potatoes

Potato flavor is improved by depth and darkness. As the potato plants grow above the soil surface, you’ll need to periodically “hill up” or mound up soil and compost around the plant so that only the top leaves stick out of the ground. It’s vital not to allow potato spuds to be exposed to sunlight, as this also causes them to turn green and produce a chemical called solanine, which gives off a bitter taste and is toxic. 

• Do the hilling in the morning, when plants are at their tallest. During the heat of the day, plants start drooping.
• Hoe dirt up around the base of the plant to cover the tubers and support the plant. 
• Check on your potatoes periodically to hill up (perhaps a few times a season).
• Stop hilling when the plant is about 6 inches tall but before the potato plant blooms.

In cool growing seasons, potato vines may sport berries. The berries are the fruit. Cut one open and see how it resembles its cousin, the tomato. Potato berries are poisonous and inedible. Plus, their seeds will not produce potato plants that resemble the parent. Discard them.

Harvesting

Harvest potatoes on dry days. Dig up gently, being careful not to puncture the tubers. Avoid cutting or bruising potato skin.

The soil should not be compacted, so digging should be easy. Potatoes can tolerate light frost, but when the first hard frost is expected, it’s time to get out the shovels and start digging potatoes.

• Harvest “new” potatoes, small ones with tender skin, 2 to 3 weeks after plants stop flowering.
• Harvest larger, mature potatoes 2 to 3 weeks after the foliage has died back. Cut down the brown foliage.

Extra tips for knowing when and how to dig up potatoes:

• Toughen up potatoes for storage before harvest by not watering them much after mid-August.
• After you cut down the brown foliage, leave the potatoes for 10 to 14 more days before you harvest. This allows the potatoes to develop a thicker skin. Don’t wait too long, though, or the potatoes may rot (especially in moisture-laden soil).
• Dig up a test hill to see how mature the potatoes are. The skins of mature potatoes are thick and firmly attached to the flesh. If the skins are thin and rub off easily, your potatoes are still too new and should be left in the ground for a few more days.
• If the soil is very wet, let the potatoes air-dry as much as possible before putting them in bags or baskets.
• Don’t leave the potatoes that you have dug in the sun for long after they have been dug up from your garden, otherwise your potatoes may turn green. Small spots can be trimmed off, but if there is significant greening, throw the potato out.

How to Cure Potatoes

• Put freshly dug potatoes in a dry, cool, place (45° to 60°F / 7° to 15°C) for up to 2 weeks. This allows the potato skin to cure and thus keep longer.
• Brush off any clinging soil; do not wash the potatoes until ready to eat; washing will shorten their life.

How to Store Potatoes

If you are harvesting potatoes to eat within a few days, storage is not an issue. You can store anywhere. To store potatoes for keeping, you need a cool (38° to 40°F), somewhat humid, dark place. Warm temperatures encourage sprouting and disease. Potatoes are 80% water so if it’s too dry, potatoes wither and dry out.

• In terms of temperature, storage options include: An extra refrigerator set a few degrees higher than normal; an unheated entrance, spare room, closet, attic, cabinet, cellar, basement, or insulated garage to protect potatoes from freezing.
• In terms of humidity: If you happen to have a damp cellar, you’ll all set! Otherwise, to elevate humidity, you could store tubers in plastic bags that are perforated (with many holes cut in the side) OR/AND placing large pans of water in front of air source. 
• To keep potatoes in the dark, use dark-colored, perforated plastic bags with many holes cut in the side to allow for air movement. Avoid all light to prevent greening.

Even after harvest, potatoes still use oxygen and give off carbon dioxide, so they must have fresh air and ventilation. Never put potatoes in airtight containers. Use perforated bags, as mentioned in steps above. 

Do not store potatoes with apples; the fruit’s ethylene gas causes spoilage.