Potatoes

History

Potato is a member of the Solanaceae family, also known as nightshades, which includes crops such as tomato, pepper, tomatillo and eggplant (Figure 1).

Potatoes are an ancient crop native to South America. According to excavations, the first recorded cultivation was by the Inca near Lake Titicaca in the Andes of Peru between 8000 and 5000 B.C. After the Spanish conquest, potatoes were carried to Europe in 1536. Sir Walter Raleigh introduced potatoes to Ireland in 1589 and it took nearly 40 years to spread throughout the rest of Europe. Potatoes returned to the Americas at the Jamestown colony in Virginia in 1621. Large plantings were established in Derry, New Hampshire, in 1719, eventually spreading across the United States to Idaho, with missionaries seeking to teach Native Americans to grow crops instead of hunting and gathering.

The ease of cultivation, high carbohydrate content and long storage quality of the potato account for its global popularity and the fact that it became an important staple of the northern European diet. Having replaced grain as the “food of the people,” it is thought to have fueled the rise of the West. The potato so increased food security in Ireland that the population doubled from 1780 to 1841. The Great Potato Famine in Ireland in the mid-1800s was caused by the reliance on the potato as a staple and crop failure due to late blight disease of potato. The famine killed a million people and led to the migration of nearly two million, with three-quarters of them going to the U.S. The reference to this crop as “Irish potato” refers to the association with Irish history, although potato is native to South America and is now grown throughout the world.

There are over 200 wild species of potato and more than 5,000 potato varieties still grown in the Andes. The Russet Burbank variety, developed in the U.S. in 1872, started the modern Idaho potato industry and is an example of the most common potato type grown in American gardens. Andean types, like blue potatoes and fingerlings, are, however, gaining in popularity.

In Louisiana, potatoes may be grown in both the fall and spring, providing a year-round supply of a highly nutritious, easily stored and prepared vegetable. The main growing season is late winter though spring as potato is a cool-season vegetable. Potatoes are planted in the late winter (January/February), in fall-prepared, well-drained soils, due to the wet weather experienced during this time. This is to take advantage of the cooler spring growing temperatures with harvest timed before high temperatures in late spring and summer. Some gardeners and small-scale growers plant a fall crop and need to rely on locally sourced tubers that are often not certified disease-free. The fall crop is often planted in suboptimal high temperatures, and in the end of the season, plants may be injured or killed by an early frost. Freeze protection, such as using row covers or temporary coverings in the garden, may be useful to extend the fall growing season.

Varieties

Potato cultivars are chosen according to cooking characteristics, yield potential, time to maturity, flesh and skin color, and storage life. Cultivars are generally classified as white, red or russet based on skin color and texture. There are thousands of cultivated varieties of potatoes in many shapes and flesh colors, including blue, gold, pink or purple flesh and various skin colors. In general, in the U.S., grocery stores now offer several types of potatoes commercially: russet, used for baking and frying (e.g., Russet Burbank); yellow with a buttery f lavor and creamy texture (Yukon Gold); red used for boiling, roasting or stewing (Red LaSoda); white for mashing or frying (Kennebec); and purple-blue fleshed f ingerlings for pan frying and roasting (Purple Peruvian). Unusual heirloom varieties are becoming more available in grocery stores, providing different colors and shapes like the fingerling, a smaller potato with a long, narrow shape. Not all cultivars can be successfully grown in Louisiana and the list of recommended cultivars is in Table 1.

One of the most commonly grown cultivars in the U.S. is Russet Burbank, which was discovered as a mutation in the early 1900s. “Russet” refers to the attractive, rough, mottled, corky periderm, or skin, that resists abrasion and damage during harvesting and transport. This variety is excellent for baking. High starch, low sugar, high specific gravity and small tuber cell size make Russet Burbank a good processing potato. Low sugar content is important because sugars often caramelize during deep frying, causing an undesirable dark-colored product in potato chips or french fries. Russet Burbank tubers can be purchased in grocery stores but are not recommended for growing in the southeastern U.S.

In Louisiana, other potato cultivars are more suitable for pan frying, boiling or using in salads, such as Red LaSoda, a cultivar developed by LSU in the 1940s. Cultivars like Red LaSoda are more suitable for boiling, having lower starch content (higher sugar) and less dry matter. They also have larger tuber cell size; smaller cells tend to slough off when boiled and often have an unsuitable texture.

Potatoes are also grouped by maturity dates as early, mid or late season. Three varieties were developed by LSU specifically for growing in Louisiana: Red LaSoda, La Rouge and LaChipper, the latter developed for the potato chip industry.

Potatoes may have different growth habits, with most varieties recommended for Louisiana being the determinate type. Determinate cultivars produce tubers close to the seed piece in a single layer. They have smaller yields and mature in less time than indeterminate cultivars. Indeterminates have the ability to form tubers up and down the stem that emerges from the seed piece, and unlike determinate varieties, shoots will continue to elongate as long as the plant is actively growing. Indeterminate varieties (i.e., La Rouge, Sebago and Purple Majesty) are the best choice for growing in towers or cages of straw or leaves. Replenishing straw as the shoots get taller will allow more tubers to form along the stem. Determinate varieties, such as Kennebec, Superior and Yukon Gold, do not have to be hilled, as all tubers will be formed at the original 4-inch planting depth. Hilling is still useful for determinate varieties to maintain a loose, friable, weed-free hill and ensure against greening. Alternatively, a heavy mulch may be applied to determinate varieties to prevent greening.

Heirloom varieties are those that have been grown and saved for at least 50 years. There are many heirloom potato varieties. Because they are always grown vegetatively instead of as seeds, heirloom potatoes are quite common and can be trusted to be true to form. See the recommended potato varieties for Louisiana in Table 1.

When and How to Plant

Potato is a frost-sensitive, cool-season annual that prefers cool temperatures for growth and development. The edible portion is actually stem tissue (a tuber) and not roots. The optimum soil temperature for tuber formation is between 60 F and 70 F. Potatoes are normally planted in the late winter. They can withstand a light frost and require a growing season of 90 to 120 frost-free days. Because tubers can’t form when soil temperatures are above 80 F, the optimal planting date is late winter in order to have a long enough growing season to harvest before the high temperatures of late spring and early summer.

Potato is vegetatively propagated, with pieces of tuber planted rather than true seeds. These are called “seed potatoes.” While any potato may be planted, certified seed potatoes are preferred because they have been grown in fields inspected to be free of infectious diseases. Certified seed is available for purchase from many hardware and feed and seed stores at the proper planting time in the late winter/early spring. Harvesting and holding seed potatoes over to plant in the fall may decrease success. It is not recommended to use potatoes purchased from grocery stores, as they are often treated with a sprout inhibitor and the cultivar may not be suitable for growing in our area. Seed potatoes should be cut into 1 1/2- to 2-inch pieces (about the size of a medium egg), with several “eyes” (sprouts) in each piece. Cut pieces may be planted immediately or kept at 60 F to 70 F for a day to heal over to reduce the incidence of rotting and disease and induce sprouting.

Plant in a well-drained row or bed. Soil temperature should ideally be 50 F, usually about three weeks before the last frost date. A soil temperature map may be helpful with planting decisions. If planted too early in the spring, seed potatoes may be slow to sprout and the tender tops may be nipped by frost, though the plant can regrow tops. Fall-planted potatoes are less sensitive to temperature and can more easily emerge in warm soils after a late summer planting. The fall crop may require occasional row covers to protect tender tops from early frosts and will produce lower yields of mostly small- to medium-sized tubers, due to a growing season cut short by the first hard freeze. Fall potatoes are more reliable in the southern part of the state than the northern part, where early freezes may interfere too much with growth.

A 4-inch-deep trench may be opened down the row, or seed pieces may be planted 4 inches deep in individual holes. Do not plant too deeply or the emergence of shoots will be delayed or tubers may rot in wet, cold soils. Plant potatoes 9 to 12 inches apart, using the closer spacing if mostly small, new potatoes are desired. Wider row spacing is helpful to allow for raking soil up onto the plants later in the season. Plant cut side down (eyes up) and cover gently with soil to avoid damaging any existing sprouts. Refer to the Potato Planting Guide (Table 2) for the recommended spacing when placing seed pieces.

Potatoes may also be planted in containers or shallowly in the ground and mounded with moist straw or mulch. Tubers will develop in the straw, aiding in easy harvest.

Table 2. Potato Planting Guide

Where to Plant

Potatoes grow best in full sun in a slightly acidic (pH 5-6), loose, amended, well-drained soil. Growing at a lower pH discourages scab, a disfiguring potato disease. Plant in beds or rows built up 10 to 12 inches tall to ensure good drainage. It is recommended to add a 2- to 3-inch layer of compost, peat, rotted hay or other organic matter and mix into the soil to optimize plant health. Although ideal planting time is late winter (January/February), this is often a time in Louisiana when soils are wet and difficult to work. To provide a well-drained bed for potatoes, prepare the ground in the fall and cover or mulch until late winter.

Each season rotate plant families — avoid planting crops from the same plant family in the same area of the garden — to reduce disease and pests. A longer crop rotation of four years is recommended for solanaceous crops like tomato, potato, eggplant and pepper to reduce pest pressure and risk of disease. It is possible to store spring potatoes for use as seed for a fall crop, but if using self-saved seed potatoes, only use for one season, then rotate back to certified seed to avoid a buildup of potato diseases.

Plant Care

It is recommended to follow sustainable gardening principles.

Growth Stages

Potatoes go through several stages of growth: sprout development, vegetative growth, tuber initiation, tuber bulking and maturation. The seed piece sprouts and shoots lengthen, then the plants grow tubers along the shoot above the seed potato. Sprouting usually takes place within 10 to 14 days (longer for the early spring crop; shorter for a fall crop). By the time the plant begins to flower, all tubers have already been formed, but will continue to increase in size until the tops of the plant naturally die down. Soil is scooped up over the stems with a hoe or rake when shoots are about 6 inches tall to encourage more tuber formation in indeterminate varieties. A second addition of soil (called “hilling”) may be done later to ensure that all tubers are well-covered. Heavy mulch may also be used for this purpose. Potatoes that become uncovered by rain and are exposed to light will turn green from chlorophyll and form a toxic alkaloid called solanine. A great deal of solanine would have to be ingested to be harmful but some people are susceptible, and greening also causes an unpleasant, bitter taste, so it should be avoided.

Watering

Potatoes are considered heavy water users and adequate moisture should be available throughout the growing season. Check for adequate soil moisture every two to three days. The soil should remain evenly moist, as uneven watering (wet, then dry) causes deformed tubers and cracking. The peak demand is during tuber initiation and tuber enlarging. Water stress during enlargement may result in irregular shaped, knobby tubers. Excessive moisture causes corky, enlarged pores in potato skins and these are more likely to rot in storage. Watering should always be done after fertilizer application to help dissolve fertilizer.

Fertilization

Do not lime to increase the pH of soils used for growing potatoes; their ideal pH is 5.5. Potatoes are heavy feeders of nitrogen. Boron deficiency can result in hollow heart, a disorder that causes cracks in the heart of the potato. A soil test, especially for micronutrients, is very useful and results may be discussed with your local county extension agent. Organic fertilizers, such as compost, fish emulsion, composted poultry litter or manure, worm castings, and blood or bone meal, originate from living organisms. They are far more environmentally sustainable and safe than traditional synthetic fertilizers. They naturally release nutrients more slowly and over a longer period of time. When applying organic fertilizer, it is important to use in unison with compost, cover crops and crop rotation, which all work together to build soil health. Learn how to convert inorganic fertilizer recommendations to organic fertilizers here.

Alternatively, a synthetic fertilizer may be used. Fertilize before planting by broadcasting and raking in 1.5 pounds of 13-13-13 per 20 feet of row. When plants are 6 to 8 inches tall, apply additional fertilizer as a sidedressing, using 0.5 to 1 pound of 13-13-13, 8-24-24 or another complete fertilizer per 20 feet of row. Sidedressing is the addition of fertilizer to the soil around already established plants when the plant begins to fruit or vine, primarily to provide nitrogen. If using synthetic fertilizer, sprinkle a small amount lightly down the side of the row, keeping it several inches away from plant stems. Water into the soil. If soil tests high for phosphorous and potassium and a complete fertilizer is not needed, calcium nitrate may be used for sidedressing at the rate of 0.4 pound per 20 feet of row. For convenience, sidedressing materials may be sprinkled on the row before hilling for the first time. Because of their slow, steady release of nitrogen, crops fertilized with organic fertilizer do not usually need to be side-dressed, but fish emulsion is a good, quick-release source of nitrogen for sidedressing heavy feeders like potatoes.

Hilling

When shoots are about 6 inches tall, scoop up dirt from the row middles to cover the plant stems, leaving the tips of stems uncovered. If growing in a raised bed, scoop from the edges of the bed. Hill again towards the end of the crop to keep potatoes near the surface well covered and protected from sunlight, which causes tuber greening.

Weeds

Because of hilling (the scooping of soil to cover plant stems several times during the season), Irish potatoes rarely have weed problems. Any weeds that escape the hilling process may be pulled by hand.

Insects, Pests and Diseases

Common insect pests include aphids, grubworms, wireworms and the Colorado potato beetle. Defects in tubers are more commonly due to physiological disorders caused by growing at higher than ideal pH (scab), excessive moisture (rough, cracked, bumpy skins) or nutrient deficiency (hollow heart). Potato is affected by some serious diseases, like late blight and several viruses. It is recommended to cover plant tops with a row cover to prevent insect pest pressure, remove old crop debris from the field and rotate annually as preventive measures. See Table 3 for diagnosis and management of common insect pests and diseases.

Table 3. Organic and Natural Management for Common Potato Pests and Diseases

Harvest and Storage

New potatoes may be harvested as soon as flowers appear, about 90 days after planting. New potatoes are immature potatoes that are sold intentionally when the skin is not completely formed and is a lighter color. Consumers often prefer these potatoes as they are easier to peel, fresher and generally have a higher sugar content suitable for pan frying or boiling, such as in crawfish boils. These may be harvested by carefully removing soil near the surface, leaving other potatoes to increase in size or to be harvested all at once.

For the regular potato crop, when tops have turned yellow and wilted, mature potatoes with thicker skins may be harvested. The vines should be allowed to mature and die before harvest so the tuber skin (periderm) is well suberized, to minimize bruising and skinning during the harvest process. Place a spading fork or shovel carefully under the plant, being cautious not to puncture the tubers or damage the skin. Lever the fork up while shaking the soil off and detach tubers from the plant’s root system. Dig when the soil is just moist; digging in wet soil will leave mud clinging to the potatoes. Brush soil from potatoes, only washing if they are very muddy, and then drying thoroughly before storing.

Tubers must be cured before storage in order to heal wounds in the skin (periderm) and to dry any soil adhering to the tubers. Tubers may be cured in a single layer or placed in bins or crates in a room or darkened place. Optimal conditions are 50 F to 68 F, and 95% to 99% humidity (the latter reduces weight loss). The curing process normally takes one to two weeks in darkness.

Potatoes can be stored, unwashed, in bins or crates in a dark, cool, moist, well-ventilated place at 45 F to 55 F and 90% relative humidity. Ideally at 45 F to 55 F and 90% relative humidity prevents starch from converting to sugar. Potatoes sold in grocery stores are normally held at low temperatures in storage (34 F to 36 F). Several days at the grocery store and room temperature converts most of the sugars back to starch. Potatoes are cured and stored in the dark to avoid greening due to light exposure. Light causes the production of chlorophyll and also the alkaloid solanine. Peeling removes most of the solanine, but it’s best to avoid greening, due to the bitter taste and sensitivity in some people.

If stored in the refrigerator, tuber starch will be converted to sugars, giving a sweet flavor and causing fried potatoes to be dark colored. Better results with refrigerated potatoes may be achieved by allowing them to sit at room temperature for several hours before cooking. Fall potatoes may be left in the cool ground to harvest as needed. Commercially, potato tubers are washed after being taken out of storage and sorted by size and placed in bags for retail sale.

Potato Is Nutritious and Good for You

High in Potassium

Essential for body function, especially the heart, kidney, nerves, bones and muscles.

Rich in Iron

Produces red blood cells.

Provides Calcium

Important for bone health.

Recipes

Basics of cooking with potatoes General information on selecting, pairing, preparing and storing. Also includes a list of recipes.

Video on how to prepare potatoes: Ever wondered about the basics of how to prepare potatoes? Chef Allison Kingery shows a couple of options for preparing this vegetable.

Other websites with many potato recipes:

Oregon State University’s Food Hero

USDA MyPlate Kitchen

Produce for Better Health Foundation

California’s Eat Fresh

Sources

• Smithsonian Magazine, November 2011. How the Potato Changed the World.
• FAO, 2008. International Year of the Potato.
• Joe Masabni. 2014. Easy Gardening: Irish Potatoes. EHT-068. Texas A&M Agrilife Extension,
• Southeastern Vegetable Extension Workers, 2024 Southeastern U.S. Vegetable Crop Handbook.
• Pack, Jeffery E., White, James M., and Hutchinson, Chad M. 2016. Growing Potatoes in Florida. HS933. University of Florida Extension,
• Potatoes. Mississippi State University Extension,
• Robinson, Andy. Potatoes 101 Powerpoint Presentation. North Dakota State University Potato Extension,
• Knuteson, Deanna. 2022. BioIPM Potato Workbook. University of Wisconsin-Madison Extension,
• Koske, Thomas J. and Cannon, James. Rev. 05/20. Louisiana Vegetable Planting Guide. Pub. 1980. LSU AgCenter.LSU AgCenter, Louisiana Vegetable Planting Guide.
• Fontenot, Kathryn, Sexton, Mary, Singh, Raj, Brown, Sebe, Strahan, Ron and Cannon, James. 2017. Vegetable Gardening Tips: Irish Potatoes. Pub. 1903. LSU AgCenter,
• Foodlink. 2020. Purdue Extension.
• McLaurin, Wayne and Reeves, Walter. (2014). How to Convert an Inorganic Fertilizer Recommendation to an Organic One. Circular 853. University of Georgia Extension.
• The Potato Association of America. 2023. North American Potato Variety Inventory,