Potato

Read about Potato in the Standard Cyclopedia of Horticulture

Potato. One of the most widely utilized and valuable of esculent tubers, produced underground as thickened stems. It is commonly known as the "Irish," "white," or "round" potato to distinguish it from the sweet potato; botanically it is Solanum tuberosum. See Solanum. The potato is one of the most universally cultivated plants of the United States and Canada, and it is becoming increasingly important as an article of human food. It ranks sixth in agricultural importance in the United States. This country produces, however, only about one-fifth as much as Germany. This is due to the fact that the German consumption of potatoes per capita is about two and a half times as great as ours, and that more than 50 per cent of the German crop is used either for stock-food or for conversion into starch, alcohol, or other industrial by-products. Potatoes, at present, are used very little for these purposes in this country, less than 1 per cent being so used. The potato is closely allied, botanically, to several powerful narcotics, such as tobacco, henbane, and belladonna, and also to tomato, eggplant, and capsicum. Potatoes contain a small amount of a somewhat poisonous substance. When exposed to the direct rays of the sun and "greened," the deleterious substance is so greatly increased that the water in which they are boiled is not infrequently used to destroy vermin on domestic animals. In any case, the water in which potatoes are cooked should not be used in the preparation of other foods. The potato is a native of the elevated valleys of Chile, Peru, and Mexico, and a form of it is found in southern Colorado. It probably was carried to Spain from Peru early in the sixteenth century. It seems to have been introduced into Europe as early as 1565. Sir Walter Raleigh, in 1585, is said to have brought back the potato from the "new country." Recent investigations, however, seem to give the credit of introducing the potato into England to Sir Francis Drake, in 1586. As Batatas virginiana, it was figured and described by Gerarde in 1597. It is probable that these circumstances led erroneously to giving the credit of introducing the potato to Raleigh instead of to Sir John Hawkins. The wild varieties in their native habitat still bear a close resemblance to cultivated varieties except for the enlarged vine and abnormal development of the tubers in the latter. In the seventeenth century the potato was cultivated in gardens in several European countries. It was recommended by the Royal Society of London in 1663 for introduction into Ireland as a safeguard against famine. The cultivation of the potato as a field crop became somewhat common in Germany soon after 1772, at which time the grain-crops failed and potatoes were a welcome substitute for the bread-corn. It was near the middle of the eighteenth century before it acquired any real importance in Europe, outside of Ireland and a few restricted localities in other countries. As late as 1771 only a white and red variety were mentioned in one of the most important English works on gardening. The plants were enormously productive, but the tubers were poor in quality, so poor in fact that their chief use was as a food for domestic animals; and only when the bread-corns failed were they used to any extent, and even then only as a substitute. By 1840 the potato had been largely substituted in Ireland for the cereals and other similar food-crops, as the yield of potatoes in weight exceeded by twenty to thirty times the yield of wheat, barley, or oats on an equal area of land. This large dependence on a single food-crop finally resulted in a wide-spread famine. The potato blight which appeared in the United States in 1845 devastated Ireland in 1846. During two years, 1846 and 1847, a conservative estimate places the numbers who perished for want of food or from diseases caused by a meager diet of unhealthy and unnutritious food at 600,000. By 1848 the plague had virtually disappeared. The roots of the potato are distinct from the tubers. Usually, two to four roots start from the stalk at the base of each underground stem which, when enlarged at the end, forms the potato. (See Fig. 3152.) Roots may also start where underground stems are wanting. The potato is a perennial plant. The accumulated starch in the tubers furnishes an abundant supply of nourishment for the plants growing from the eyes or buds until they are well above the ground. So much food is stored that not infrequently small young tubers are formed on the outside of the potatoes left in the cellar during the summer. Potatoes grow from 2 to even 3 feet high, have smooth, herbaceous stems, irregularly pinnate leaves, and wheel-shaped flowers, varying in breadth from 1 to 1 1/2 inches and in color from bluish white to purple. They bear a globular purplish or yellowish fruit or seed-ball of the size of a gooseberry, containing many small seeds. As many as 297 seeds have been found in a single seed-ball. The cultivated potato of today has undergone a remarkable change since its first introduction into Europe by the Spaniards. Some of this change has been brought about by better cultivation, but most of it is due to breeding. The tubers of the wild S. tuberosum were small and attracted little attention. Heriot, in his report on Virginia, describes the plant "with roots as large as a walnut and others much larger ; they grow in damp soil, many hanging together as if tied on ropes." The modern potato has been bred so that the hills contain four to six tubers of uniform size, weighing, perhaps, two pounds. (See Fig. 3153.) The uses of the potato are wide and varied, but taking the world over, its greatest value is as a food-crop. It is probably eaten by a greater proportion of the earth's inhabitants than any other crop except rice. It is extensively used for the manufacture of starch. The great potato-growing sections of the United States, especially Aroostook County, Maine, have many starch factories, where the tubers which are oversize or under- size or otherwise not fitted for ordinary food purposes are converted into starch. The price ordinarily paid for potatoes for starch-making is considerably less than that for eating, and unions the price for eating gets very low, good marketable tubers are not used for starch. The potato has many other uses which have been much less developed in the United States than in Europe, but there is a rapidly increasing tendency for their uses in the arts here. It is used in the textile industries, in the manufacture of woolen, linen, and silk goods; for the manufacture of potato flour, glucose, syrup, candy, desiccated potatoes for food, industrial alcohol, mucilage, dyes, stock-feed, and so forth. The dry matter of potatoes is composed largely of starch. A high starchy content is desirable because it makes a mealy potato which is demanded in America. Being deficient in nitrogen, the potato is ill adapted for an exclusive diet and should be used in connection with food containing a high percentage of proteids, such as lean meat, peas, beans, and eggs. The lack of vegetable fats may be supplied by butter, gravy, or oatmeal. The composition of the potato varies widely. An average of 136 analyses is as follows: Water Ash Protein Starch Fat Per Per Per Per Per cent cent cent cent cent Potatoes. . . . .78. 1. 2.2 18. .1 Oatmeal. . . . . 7.9 2. 14.7 67.4 7.1 Graham flour. . . 13.1 1.8 11.7 69.8 1.7 The nutritive ratio of wheat is 1 to 5.37, almost perfect; that of potatoes 1 to 18.29, much too wide. Many foods in their natural state, as potatoes, are more or less deficient in mineral matter. Notable among these are rice and wheat flour ,the former containing but 0.4 per cent and the latter 0.5 per cent of ash. The main potato industry in the United States is confined to several potato-growing sections in widely separated parts of the United States. The most important of these are Aroostook County, Maine; the Norfolk and Eastern Shore trucking regions of Virginia and Maryland; the Red River Valley of Minnesota and North Dakota; the Kaw Valley of Kansas; the Greely and Carbondale districts of Colorado; the Twin Falls country of Idaho, and the San Joaquín and Sacramento valleys of California. In these regions, the climate and soil are perfect for the best potato- production. Varieties. There are many hundred varieties of potatoes. The older varieties run out in the course of time and are supplanted by new ones. The running out is largely due to the fact that growers, as a rule, do not practise seed-selection. The new varieties are ordinarily produced either from hybridized seed or from bud-sports. The latter are somewhat common. Red tubers are now and then found in white hills, and vice versa. Other differences are taken advantage of by breeders. Of the many varieties listed in seedsmen's catalogues and found on the market, however, only a very few are of commercial importance. Fitch, of the Iowa State College, has made a thorough trial for a number of years of all varieties of commercial importance in the Unites States and Europe. He also made a canvass in person and by letter of the markets of the United States. The result was that only a few varieties were found to be of much market value. He lists the following varieties as being the most valuable in the United States in order of their importance: Rural New Yorker, Green Mountain, Early Ohio, Burbank, Irish Cobbler, Bliss Triumph, Peerless (Pearl). Many other varieties, of course, have local importance and perhaps outyield the standard varieties named above. New varieties are being produced constantly, a very few of which may prove to be better than the standard sorts, but most of them are worthless. William Stuart, of the United States Department of Agriculture, has recently made a very comprehensive and admirably arranged classification of potatoes, as follows : Group 1. Cobber. Tubers: Roundish; skin creamy white. Sprouts: Base, leaf- scales, and tips slightly or distinctly tinged with reddish violet or magenta. In many cases the color is absent. Flowers: Light rose- purple; under intense heat may be almost white. Group 2. Triumph. Tubers: Roundish; skin creamy white, with more or less numerous splashes of red, or carmine, or solid red; maturing very early. Sprouts: Base, leaf-scales, and tips more or less deeply suffused with reddish violet. Flowers: Very light rose-purple. Group 3. Early Michigan,. Tubers: Oblong or elongate-flattened; skin white or creamy white, occasionally suffused with pink around bud-eye cluster in Early Albino Sprouts: Base light rose-purple; tips creamy or light rose-purple. Flowers: White. Group 4. Rose. Tubers: Roundish oblong to elongate-flattened or spindle- shape flattened; skin flesh-colored or pink, or (in the case of the White Rose) white. Sprouts: Base and internodes creamy white to deep rose-lilac; leaf-scales and tips cream to rose-lilac. Flowers: White in sections 1 and 2; rose-lilac in section 3. Group 5. Early Ohio. Tubers: Round, oblong, or ovoid; skin flesh-oolored or light pink, with numerous small, raised, russet dots. Sprouts: Base, leaf-scales, and tips more or less deeply suffused with carmine-lilac to violet-lilac or magenta. Flowers: White. Group 6. Hebron. Tubers: Elongated, somewhat flattened, sometimes spindle- shaped; skin creamy white, more or less clouded with flesh-color or light pink. Sprouts: Base creamy white to lilac; leaf-scales and tips pure mauve to magenta, but color sometimes absent. Flowers: White, Group 7. Burbank. Tubers: Long, cylindrical to somewhat flattened, inclined to be slightly spindle-shaped; skin white to light creamy white, smooth, and glistening, or deep russet in the case of section 2. Sprouts: Base creamy white or faintly tinged with magenta; leaf-scales and tips usually lightly tinged with magenta. Flowers: White. Group 8. Green Mountain. Tubers: Moderately to distinctly oblong, usually broad, flattened; skin a dull creamy or light russet color, frequently having russet-brown splashes toward the seed end. Sprouts: Section 1 base, leaf-scales, and tips creamy white: section 2 base usually white, occasionally tinged with magenta: leaf-scales and tips tinged with lilac to magenta. Flowers: White, Group 9. Rural. Tubers: Broadly round-flattened to shortroblong, or distinctly oblong-flattened; skin creamy white, or deep russet in the case of section 20. Sprouts: Base dull white; leaf-scales and tips violet- purple to pansy-violet. Flowers: Central portion of corolla deep violet, with the purple growing lighter toward the outer portion; five points of corolla white, or nearly so. Group 10. Pearl Tubers: Round-flattened to heart-shape-flattened, usually heavily shouldered; skin dull white, dull russet, or brownish white in section 1 or a deep bluish purple in section 2. Sprouts: Section 1 base, leaf-scales, and tips usually faintly tinged with lilac; section 2 base, leaf-seal , and tips vinous mauve. Flowers: White. Group 11. Peachblow. Tubers: Round to round-flattened or round-oblong; skin creamy white, splashed with crimson or solid pink: eyes usually bright carmine. Includes some early-maturing varieties. Sprouts: Base, leaf-scales, and tips more or less suffused with reddish violet. Flowers: Purple. Cultivation of potatoes. The best soil for potatoes is a sandy loam, well drained but provided with an abundant supply of water. If the soil is deficient in moisture, the water from rainfall must be conserved by shallow cultivation. The ground should be plowed deeply and worked thoroughly so as to bring about perfect aeration. Whether the plowing should be done in the fall or the spring will depend largely upon the distribution of time and labor which the grower has at his disposal, except that hilly fields which are likely to wash during winter should not be plowed in the fall. In cutting potatoes for planting, each eye should be supplied with an abundance of food to start the young plants vigorously. The pieces should be as large as possible and not bear more than piece two or three eyes. (See Fig. 3154.) The potato is sensitive to frost, and therefore must complete its growth in most localities in three to six months. The period of development may be shortened by exposing the seed potatoes to the more or less direct rays of the sun in a temperature of about 60° for one or two weeks before planting. Some of the starch is transformed into sugar, which causes the eyes or buds to develop into miniature short tough plants or "rosettes" which results, when the potatoes are planted, in hastening growth and shortening the period between planting and harvesting. Some varieties, when thus treated in warm rich sandy soil, produce merchantable tubers in six weeks. The kind and amount of fertilizer which should be applied to potatoes will, of course, vary with conditions, such as method of rotation, natural fertility of the land, methods of growing the crop and so forth. The best method of rotation is one in which a crop of clover immediately precedes the potato-crop, particularly in the North. This furnishes nitrogen and leaves the ground in good mechanical condition. Ordinarily, potatoes require a fertilizer analyzing about 4 per cent of potash, 7 per cent of phosphoric acid and 10 per cent of potash. If lime is applied to the land during the rotation, it should follow the potatoes and not precede them, as it furnishes the best conditions for the development of scab, which is a serious disease. The same is true of wood-ashes which, ordinarily, contain 30 per cent of lime. Potatoes are planted either by hand or with a machine. Good-sized tubers should be cut into about four pieces and a single piece placed in each hill. The seed-pieces should be planted soon after cutting so as to prevent "bleeding or loss of water from the cut surfaces. The depth of planting will depend upon circumstances, but ordinarily 4 to 6 inches maybe considered an average depth. The planting-machines are usually drawn by two horses and perform several operations at once. They open the furrow, distribute the fertilizer, cover it slightly so that it will not come into direct contact with the seed, drop the seed-pieces and cover them. Sometimes a heavy wheel, to act as a roller, is attached to the rear of the machine to pack the soil over the hills. By means of these machines, large acreages may be planted in a short time. Potato fields should be given frequent and thorough tillage to keep down the weeds and conserve soil moisture. These cultivations should be shallow to prevent injury to the roots. The soil is cultivated until the plants are large enough nearly to fill the rows and have begun to "set" tubers. Further tillage is likely to injure the plants and reduce the yield. After the plants are mature, the tubers are dug either by hand or with an elevator digger drawn by two or more horses. Yields. The yield of potatoes to the acre in the United States is meager, the average yield for the ten-year period 1900-1909 being 91.4 bushels. Under favorable soil and climatic conditions, with rational methods of procedure, 200 to 400 bushels are not uncommon, and under superior conditions more than 1,000 bushels to the acre have been secured. By dividing the eyes and planting them in the greenhouse in the winter, and after a little time re-dividing them, continuing this until many plants were secured, one grower was enabled to raise 2,558 pounds of potatoes in the open from one pound of seed, being an increase of more than 2,500 fold. Two other growers secured, by similar methods, 2,349 pounds and 2,118 pounds. The low average yield is due, in part, to the ravages of the many enemies of the potato plant, which, uncontrolled, sometimes destroy the crop, and usually seriously diminish the yield. In the United States, the potato is not so universally used or so productive as in Europe, though its use as a food is steadily increasing. In common commercial culture, the yield as well as quality may be greatly enhanced by care in selecting seed. The progeny of two similar potatoes is shown in Fig. 3153, showing the inherited performance of the tubers. The average annual production in the United States from 1881 to 1890 was 169,809,053 bushels, while the yield in 1913 was 331,525,000 bushels, which sold for an average farm price of 48.9 cents a bushel. New York stands first in potato-production, producing 53,215,000 bushels of the total yield. The crop of Europe aggregates more than the entire wheat-crop of the world. The production of the European countries for 1913 was: France, 477,111,000; Austria, 424,457,000; Germany, 1,988,591,000; Russia, 1,274,439,000; the United Kingdom, 283,912,000 bushels. In 1912 the United States exported 76,382,000 bushels and imported 80,134,000 bushels. Enemies. The most common enemy to the potato plant, the Colorado potato-bug, is easily destroyed by applications in a powder or in a liquid of paris green or arsenate of lead to the vines when the bugs first appear. The fungus, Phytophthora infestans, causes the true blight (Fig. 3155), which results in potato-rot. The true blight may be kept in check by frequent and thorough sprayings with bordeaux mixture. It is always well to incorporate arsenicale with the mixture, that any remaining bugs may be destroyed. The bordeaux mixture is also useful in protecting in part the plants from the flea-beetle. Two or three applications are usually made during the summer. The early blight is more common than the true or late blight. It causes the shriveling and death of the foliage (Fig. 3155). It is usually the combined result of several causes, chief amongst which are fungi, flea-beetle, drought. Thorough good care and spraying with bordeaux mixture are the best treatments. A good potato field is shown in Fig. 3156 (adapted from "American Agriculturist"); and the picture also shows a good hand-praying rig. A. W. Gilbert. Potatoes as a market-garden or truck crop. The chief difference between potatoes as a field crop and a market-garden or truck-farm crop is that in the former case they are grown in rotation with other long- season plants and consequently may occupy the ground for the entire growing season, while in the latter they occupy the ground only a few weeks and are usually preceded and followed by some early or late garden crop the same year. In the North the crop is usually grown in the spring and early summer, but in the South it may be grown either in the early spring or late fall. The spring crop is grown to supply the demand for new potatoes in the early markets while prices are high, but the fall crop is mostly consumed locally either for table purposes or for seed for the next spring crop. In the trucking region of the upper South, the spring crop is planted in January, February, or March and harvested in May and June, and the fall crop in July or August and harvested in October or November. The favorite Virginia rotation starts with potatoes planted in February and harvested in June. Cowpeas are sown immediately for a summer cover-crop; these are plowed under in August as a means of improving the soil, and spinach is planted in September. This crop is harvested in January or February and garden peas are planted in rows 5 or 6 feet apart. The peas are inter- planted in late March with cucumbers. The peas are harvested in April and May, and the cucumbers in June and July. The ground is planted to kale in August, which is harvested in midwinter and potatoes planted again in February or March. A second two year rotation starts with potatoes planted in February followed by cowpeas or an annual grass for forage. Winter cabbage is transplanted to the field in November or January. Corn is planted after the cabbage is harvested in May or June. Cowpeas are planted between the rows of corn at the last working. The cornstalks remain standing in the field until late fall when the grain is harvested and they and the pea-vines are worked into the ground to supply organic matter. Since earliness, productiveness, and reasonable resistance to disease are the main requisites for truck- farm potatoes, the varieties that meet the requirements are limited. In the South Atlantic and Gulf states, Bliss Triumph is the leading variety, while in the Carolinas and Virginia, Irish Cobbler is the favorite; but in the upper Mississippi Valley, Early Ohio undoubtedly is in the lead. Seed grown in Maine, Michigan, Wisconsin, or other northern states will produce potatoes of marketable size five to ten days earlier than locally grown seed. Consequently truck-farmers who wish to cater to the early market depend upon the northern tier of states for their seed-supply; but those who wish to sell on the midseason market are now largely using locally grown seed. Plants from northern-grown seed suffer more severely from certain diseases than do those from local seed, hence the extreme earliness of the crop from the northern seed is, to a marked degree, compensated for by the healthier vines and larger yield from local seed. The seed-stock to be used in producing the home or locally grown seed is obtained from the North in the winter or early spring, and held in cold storage until July or August, when it is planted. The tubers are harvested after the vines are killed by frost in October or November, and are placed in farm storage until needed for planting. The land should be broken with a turn-plow a month or six weeks in advance of planting the potatoes, if the preceding crop in the rotation will admit. It is best to apply the stable-manure to some preceding crop in order that it may be well decayed before the tubers are planted. After the ground is thoroughly harrowed, the rows should be marked out about 3 feet apart. If drainage is not good it is well to open the furrow with a small turning-plow in order to expose a large surface to the action of the sun, air, and frost. A few days before planting, the furrows should be reopened, the fertilizer required distributed in them. It should be thoroughly mixed with the soil to prevent its coming into direct contact with the seed-tubers when they are planted. In forcing potatoes, especially in the cooler season of the year, it is customary to use from 1,500 pounds to 2,000 pounds of fertilizer analyzing 5 to 6 per cent nitrogen, 6 to 7 per cent phosphoric acid, and 5 per cent potash, to the acre. The potatoes will not use all of this, but that remaining after they are harvested is available for subsequent crops. About one-third of the nitrogen in the fertilizer should be obtained from nitrate of soda and sulfate of ammonia and the other two- thirds from high-grade tankage, blood, and fish-scrap. By using nitrogen from the sources mentioned, the plants are enabled to obtain a constant supply throughout their growing-season. The phosphoric acid is obtained from acidulated South Carolina rock, and the potash, preferably, from sulfate of potash. Some growers apply about 1,000 pounds of the fertilizer in the rows before the tubers are planted and the balance as a side or top dressing when the plants are well started. Whether the potatoes are to be planted by hand or a power planter, it is better to apply the fertilizer before planting, as much better distribution may thus be obtained. The larger number of truck-farmers follow the practice of hand planting, but the larger growers are now using horse-power machines. From three to five barrels of northern-grown seed and from two to three barrels of home-grown seed are usually required to plant an acre. The seed-pieces are placed 14 to 16 inches apart in the rows and are usually placed from 2 to 4 inches below the surface-level of the ground. The hand-planted tubers are covered by turning two furrows over them with a small turn-plow, thus forming a ridge 8 or 9 inches high above the tubers. If the discs of the power planter do not form such ridges, it is customary to add additional soil with the plow. These high ridges protect the seed-tubers against unfavorable weather conditions and enables them to develop strong roots before the sprouts appear above the ground, thus insuring rapid development when the season opens. As soon as the tubers have formed sprouts an inch or two long, a light harrow is dragged diagonally across the ridges to kill any weeds that may be starting, and to provide a mulch over the row. A second dragging is given a week or ten days later, or just before the sprouts appear above the surface. The first working with the cultivator is given as soon as the plants have the row well outlined; subsequent cultivations are given at intervals of a week or ten days, a small quantity of soil being worked against the plants, thus forming low ridges at the later cultivations. If proper attention is given to the early cultivation, little or no hoe work need be expected. The season for harvesting depends more upon market conditions than upon the maturity of the crop. If prices are high, digging may be started when the yield will not be over thirty or forty barrels to the acre, but if prices are moderate with indications for a steady demand, harvesting may be delayed for two or three weeks. In the meantime the yield will have increased from 25 to 50 per cent. The crop is usually turned out of the ground with a plow while the vines are still green. The vines are then pulled out of the ground with most of the tubers attached. These are carefully pulled from the roots, the others picked out of the loose soil and placed into piles on the ground. They are then graded by hand and packed in barrels for shipment. Great care is used in handling the new potatoes to prevent unnecessary bruising. Mechanical diggers have not given satisfaction in the trucking region of the South, primarily because they bruise and break the skin, thus causing the tubers to present discolorations when placed on the market. T. C. Johnson. Potato, air: Dioscorea bulbifera. P. Onion: Onion. P., Sweet: Sweet Potato, and Ipomaea Batatas. The above text is from the Standard Cyclopedia of Horticulture. It may be out of date, but still contains valuable and interesting information which can be incorporated into the remainder of the article. Click on "Collapse" in the header to hide this text.

? Potato
Plant Info
Scientific classification
Kingdom: Plantae Division: Magnoliophyta Class: Magnoliopsida Sublass: Asteridae Order: Solanales Family: Solanaceae Genus: Solanum Species: S. tuberosum
Binomial name
Solanum tuberosum L.

The potato (Solanum tuberosum) is a perennial plant of the Solanaceae, or nightshade, family, commonly grown for its starchy tuber. Potatoes are the world's most widely grown tuber crop, and the fourth largest crop in terms of fresh produce — after rice, wheat, and maize ('corn'). The potato originated in southern Peru and is important to the culture of the Andes, where farmers grow many different varieties that have a remarkable diversity of colors and shapes. Potatoes spread from the Americas to the rest of the world after European colonization in the late 1400s and early 1500s and have since become an important field crop. The potato is also often strongly associated with Idaho, Prince Edward Island, Ireland and Russia, after having been adopted by these regions after the Columbian Exchange. However, it is native to Peru and was first cultivated by the Incas.

Botanical description

Flowers of a potato plant.

Potato plants have a low-growing habit and bear white to purple flowers with yellow stamens.

Potato plant

Potato varieties bear flowers containing asexual parts. Flowers are mostly cross-pollinated by other potato plants, including by insects, but a substantial amount of self-fertilizing occurs. Any potato variety can also be propagated vegetatively by planting pieces of existing tubers, cut to include at least one or two eyes. Some commercial varieties of potatoes do not produce seeds at all (they bear imperfect, single-sex flowers) and are propagated only from tuber pieces. Confusingly, these pieces can bear the name "seed potatoes". After potato plants flower, some varieties will produce small green fruit that look similar to green cherry-tomatoes. These produce seeds like other fruits. Each of the fruits can contain up to 300 true seeds. One can separate seeds from the fruits by putting them in a blender on a slow speed with some water, then leaving them in water for a day so that the seeds will sink and the rest of the fruit will float. However, some horticulturists sell chimeras made by grafting a tomato plant onto a potato plant, which can produce both edible tomatoes and potatoes.

Food value

Nutritionally, potatoes are best known for their carbohydrate content (approximately 26 grams in a medium potato). Starch is the predominant form of carbohydrate found in potatoes. A small but significant portion of the starch in potatoes is resistant to enzymatic digestion in the stomach and small intestine and, thus, reaches the large intestine essentially intact. This resistant starch is considered to have similar physiological effects and health benefits of fiber (e.g., provide bulk, offer protection against colon cancer, improve glucose tolerance and insulin sensitivity, lower plasma cholesterol and triglyceride concentrations, increase satiety, and possibly even reduce fat storage) (Cummings et al. 1996; Hylla et al 1998; Raban et al. 1994). The amount of resistant starch found in potatoes is highly dependent upon preparation methods. Cooking and then cooling potatoes significantly increases resistant starch. For example, cooked potato starch contains about 7% resistant starch, which increases to about 13% upon cooling (Englyst et al. 1992).

Potatoes contain a number of important vitamins and minerals. A medium potato (150g/5.3 oz) with the skin provides 27 mg vitamin C (45% of the Daily Value (DV)), 620 mg of potassium (18% of DV), 0.2 mg vitamin B6 (10% of DV) and trace amounts of thiamin, riboflavin, folate, niacin, magnesium, phosphorus, iron, and zinc. Moreover, the fiber content of a potato with skin (2 grams) equals that of many whole grain breads, pastas, and cereals. In addition to vitamins, minerals and fiber, potatoes also contain an assortment of phytochemicals, such as carotenoids and polyphenols. The notion that “all of the potato’s nutrients” are found in the skin is a myth. While the skin does contain approximately half of the total dietary fiber, the majority (more than 50%) of the nutrients are found within the potato itself. The cooking method used can significantly impact the nutrient availability of the potato.

New and fingerling potatoes offer the advantage that they contain fewer toxic chemicals. Such potatoes offer an excellent source of nutrition. Peeled, long-stored potatoes have less nutritional value, although they still have potassium and vitamin B.

Potatoes are often broadly classified as “high” on the glycemic index (GI) and thus are frequently excluded from the diets of individuals trying to follow a “low GI” eating regimen. In fact, the GI of potatoes can vary considerably depending on the type (i.e., red vs. russet vs. white vs. Prince Edward), origin (i.e., where it was grown), preparation methods (i.e., cooking method, whether it is eaten hot or cold, whether it is mashed or cubed or consumed whole, etc), and what it is consumed with (i.e., the addition of various high fat or high protein toppings) (Fernandes et al. 2006).

Cooking

Various potato dishes.

General methods

Potatoes are prepared in many ways: skin-on or peeled, whole or cut up, with seasonings or without. The only requirement involves cooking to break down the starch. Most potato dishes are served hot, but some are first cooked then served cold, notably potato salad and potato chips/crisps.

Common dishes are: mashed potatoes, which are first boiled (usually peeled), and then mashed with milk and butter; whole baked potatoes; boiled or steamed potatoes; French-fried potatoes or chips; cut into cubes and roasted; scalloped, diced, or sliced and fried (home fries); grated into small thin strips and fried (hash browns); grated and formed into dumplings, Rösti or potato pancakes. Unlike many foods, potatoes can also be easily cooked in a microwave oven and still retain nearly all of their nutritional value, provided that they are covered in ventilated plastic wrap to prevent moisture from escaping—this method produces a meal very similar to a baked potato. Potato chunks also commonly appear as a stew ingredient.

Regional dishes

Peruvian Cuisine naturally contains the potato as a primary ingredient in many dishes, as over 9,000 varietiesTemplate:Fact of this tuber are grown there. Some of the more famous dishes include Papa a la huancaina, Papa rellena, Ocopa, Carapulcra, Causa and Cau Cau among many others.

Mashed potatoes form a major component of several traditional dishes from the British Isles such as shepherd's pie, bubble and squeak, champ and the 'mashit tatties' (Scots language) whi ch accompany haggis. They are also often sautéed to accompany a meal.

Colcannon is a traditional Irish dish involving mashed potato combined with shredded cabbage and onion.

Potatoes are very popular in continental Europe as well. In Italy, they serve to make a type of pasta called gnocchi. Potatoes form one of the main ingredients in many soups such as the pseudo-French vichyssoise and Albanian potato and cabbage soup.

In the United States, potatoes have become one of the most widely consumed crops, and thus have a variety of preparation methods and condiments. One popular favorite involves a baked potato with cheddar cheese (or sour cream and chives) on top, and in New England "smashed potatoes" (a chunkier variation on mashed potatoes, retaining the peel) have great popularity.

In Northern Europe, especially Denmark, Sweden and Finland, newly harvested, early ripening varieties are considered a special delicacy. Boiled whole and served with dill, these "new potatoes" are traditionally consumed together with Baltic herring.

A traditional Canary Islands dish is Canarian wrinkly potatoes or Papas arrugadas.

A traditional Acadian dish from New Brunswick is known as poutine râpée. The Acadian poutine is a ball of grated and mashed potato, salted, sometimes filled with pork in the centre, and boiled. The result is a moist ball about the size of a baseball. It is commonly eaten with salt and pepper or brown sugar. It is believed to have originated from the German Klöße, prepared by early German settlers who lived among the Acadians.

Poutine, by contrast, is a hearty serving of french fries, fresh cheese curds and hot gravy. Tracing its origins to Quebec in the 1950s, it has become popular across Canada and can usually be found where Canadians gather abroad.

Toxic compounds in potatoes

Potato plants

Potatoes contain glycoalkaloids, toxic compounds, of which the most prevalent are solanine and chaconine. Cooking at high temperatures (over 170 °C or 340 °F) partly destroys these. The concentration of glycoalkaloid in wild potatoes suffices to produce toxic effects in humans. Glycoalkaloids occur in the greatest concentrations just underneath the skin of the tuber, and they increase with age and exposure to light. Glycoalkaloids may cause headaches, diarrhea, cramps and in severe cases coma and death; however, poisoning from potatoes occurs very rarely. Light exposure also causes greening, thus giving a visual clue as to areas of the tuber that may have become more toxic; however, this does not provide a definitive guide, as greening and glycoalkaloid accumulation can occur independently of each other. Some varieties of potato contain greater glycoalkaloid concentrations than others; breeders developing new varieties test for this, and sometimes have to discard an otherwise promising cultivar.

Breeders try to keep solanine levels below 0.2 mg/g (200 ppmw). However, when even these commercial varieties turn green, they can approach concentrations of solanine of 1 mg/g (1000 ppmw). Some studies suggest that 200 mg of solanine can constitute a dangerous dose. This dose would require eating 1 average-sized spoiled potato or 4 to 9 good potatoes (over 3 pounds or 1.4 kg) at one time. The National Toxicology Program suggests that the average American consumes at most 12.5 mg/person/day of solanine from potatoes. Dr. Douglas L. Holt, the State Extension Specialist for Food Safety at the University of Missouri - Columbia, notes that no reported cases of potato-source solanine poisoning have occurred in the U.S. in the last 50 years and most cases involved eating green potatoes or drinking potato-leaf tea.

Solanine is also found in other plants, in particular the deadly nightshade. This poison affects the nervous system causing weakness and confusion.

Seed tuber with sprouts
Early Rose variety

Potato Planting
Washington

See also

• Solanine
• List of poisonous plants
• Sites with information about the safety of green potatoes:
  • http://health.yahoo.com/topic/nutrition/foods/qanda/mayoclinic/0F1A15E7-8E68-42DD-855A3ACEDA510E13
  • http://www.straightdope.com/classics/a2_055b.html
  • http://www.foodscience.afisc.csiro.au/spuds.htm
  • http://www.promolux.com/english/retail_produce_greening.html

Cultivation

Potatoes are generally grown from the eyes of another potato and not from seed. Home gardeners often plant a piece of potato with two or three eyes in a hill of mounded soil. Commercial growers plant potatoes as a row crop using seed tubers, young plants or microtubers and may mound the entire row.

At harvest time, gardeners generally dig up potatoes with a long-handled, three-prong "grape" (or graip), i.e. a spading fork, or a potato hook which is similar to the graip, except the tines are at a 90 degree angle to the handle as is the blade of a hoe. In larger plots, the plough can serve as the most expeditious implement for unearthing potatoes. Commercial harvesting is typically done with large potato harvesters which scoop up the plant and the surrounding earth. This is transported up an apron chain consisting of steel links several feet wide. This separates some of the dirt. The chain deposits into an area where further separation occurs. Different designs employ different systems at this point. The most complex designs use vine choppers and shakers, along with a blower system or "Flying Willard" to separate the potatoes from the plant. The result is then usually run past workers who continue to sort out plant material, stones, and rotten potatoes before the potatoes are continuously delivered to a wagon or truck. Further inspection and separation occurs when the potatoes are unloaded from the field vehicles and put into storage.

Correct potato husbandry is a most arduous task in the best of circumstances. Correct harrowings, plowings, and rollings are always needed, along with a little grace from the weather. Indeed, potatoes are the most fruitful of the root-weeds, but much care and consideration is needed to keep them satisfied and thus fruitful.

Eliminating all root-weeds is desirable in potato cultivation. Three plowings, with necessary harrowings and rollings, are desirable if they can be accomplished before the appropriate planting time.

It is important to harvest potatoes before heavy frosts begin, since field frost damages potatoes in the ground, and even cold weather makes potatoes more susceptible to bruising and possibly later rotting which can quickly ruin a large stored crop.

Seed potato crops are 'rogued' in some countries to eliminate diseased plants or those of a different variety from the seed crop.

Potato field
Fort Fairfield, Maine

Pests

A major pest of potato plants is the Colorado potato beetle.

The potato root nematode is a microscopic worm that thrives on the roots, thus causing the potato plants to wilt. Since its eggs can survive in the soil for several years, crop rotation is recommended.

Other pests include Aphids, both the Green Peach Aphid and the Potato Aphid. Beetleafhoppers, Thirps, and Mites are also very common potato insect pests.

Diseases

Main article: List of potato diseases

A major disease of potato plants is potato blight caused by Phytophthora infestans.

Other major diseases include Rhizoctonia, Sclerotinia, Black Leg, Powdery Mildew, Powdery Scab, Leafroll Virus, Purple Top, and others.

New potatoes

Potatoes are generally cured after harvest to thicken the skin. Prior to curing, the skin is very thin and delicate. These potatoes are known as "New Potatoes" and are particularly flavorful. New potatoes are often harvested by the home gardener by "grabblin g", i.e. pulling out the young tubers by hand while leaving the plant in place. In markets one sometimes finds thin-skinned varieties sold as new potatoes.

Storage

Storage facilities need to be carefully designed to keep the potatoes alive and slow the natural process of decomposition, which involves the breakdown of starch. It is crucial that the storage area is dark, well ventilated and for long-term storage maintained at temperatures near 40ºF (4ºC). For short-term storage prior to cooking, temperatures of about 45-50°F (7-10°C) are preferred. Temperatures below 40°F (4°C) convert potatoes' starch into sugar, which alters their taste and cooking qualities and leads to higher acrylamide levels in the cooked product, especially in deep-fried dishes. Potatoes may be kept in the crisper (high-humidity) drawer of a refrigerator, but should be removed and kept in warmth for a few days before use (to allow the sugar to convert back to starch). Under optimum conditions possible in commercial warehouses, potatoes can be stored for up to six months, but several weeks is the normal shelflife in homes. If potatoes develop green areas or start to sprout, these areas should be trimmed before using.

Notes

Maine companies are exploring the possibilities of using waste potatoes to obtain polylactic acid for use in plastic products.

Trivia

• The Norwegian municipality of Østre Toten has a potato plant in its coat-of-arms.
• Potatoes were first documented in Scotland in 1701 when the Duchess of Buccleuch recorded in her household book the purchase of a peck at 2/6d (Gauldie 1981).
• The potato is called pomme de terre in French, aardappel in Dutch, and sometimes Erdapfel in German, all literally "apple of the earth".
• Different names for the potato developed in China's various regions, the most widely used names in standard Chinese today are "horse-bell yam" (马铃薯 - mǎlíngshǔ), "earth bean" (土豆 - tǔdòu), and "foreign taro" (洋芋 - yángyù).
• Although traditionally known for its value as a food product, the potato has come to find more popularity as ammunition for devices commonly called Potato Cannons, Spud guns, or "Spudzookas."

See also

• Potatoe, archaic spelling
• Sweet potato, distantly related to the potato
• Chuño, traditional freeze-dried potato of Altiplano

Further reading

• Larry Zuckerman (1999). Potato, The: How the Humble Spud Rescued the Western World. Douglas & McIntyre. ISBN 0-86547-578-4.
• Lang, James (2001). Notes of a Potato Watcher, Texas A&M University, College Station, TX.
• Salaman, Redcliffe N. (1989). The History and Social Influence of the Potato, Cambridge University Press (originally published in 1949; reprinted 1985 with new introduction and corrections by J.G. Hawkes).
• Hawkes, J.G. (1990). The Potato: Evolution, Biodiversity & Genetic Resources, Smithsonian Institution Press, Washington, D.C.
• Stevenson, W.R., Loria, R., Franc, G.D., and Weingartner, D.P. (2001) Compendium of Potato Diseases, 2nd ed, Amer. Phytopathological Society, St. Paul, MN.

References and external links

Footnote References

• Spooner, David; et al. (October 2005). [http://www.pnas.org/cgi/content/full/102/41/14694 "A single domestication for potato based on multilocus amplified fragment length pol

ymorphism genotyping"]. Proc. Natl. Acad. Sci. USA 102 (41): 14694-14699. doi:10.1073/pnas.0507400102. http://www.pnas.org/cgi/content/full/102/41/14694. 

• World Geography of the Potato at http://www.lanra.uga.edu/potato/
• mr Travers
• Reference for potato history: The Vegetable Ingredients Cookbook by Christine Ingram, Lorenz Books, 1996 ISBN 1-85967-264-7
• The History and Social Influence of the Potato by Redcliffe N. Salaman ISBN 0-521-31623-5
• Hamilton, Andy & Dave, (2004), Potatoes - Solanum tuberosums retrieved on 4 May 2005
• Cummings JH, Beatty ER, Kingman SM, Bingham SA, Englyst HN. Digestion and physiological properties of resistant starch in the human large bowel. Br J Nutr. 1996;75:733-747.
• Englyst HN, Kingman SM, Cummings JH. Classification and measurement of nutritionally important starch fractions. Eur J Clin Nutr. 1992;46:S33-S50.
• Fernandes G, Velangi A, Wolever TMS. Glycemic index of potatoes commonly consumed in North America. J Am Diet Assoc. 2005;105:557-62.
• Gauldie, Enid (1981). The Scottish Miller 1700 - 1900. Pub. John Donald. ISBN 0-85976-067-7.
• Hylla S, Gostner A, Dusel G, Anger H, Bartram HP, Christl SU, Kasper H, Scheppach W. Effects of resistant starch on the colon in healthy volunteers: possible implications for cancer prevention. Am J Clin Nutr. 1998;67:136-42.
• Raban A, Tagliabue A, Christensen NJ, Madsen J, Host JJ, Astrup A. Resistant starch: the effect on postprandial glycemia, hormonal response, and satiety. Am J Clin Nutr. 1994;60:544-551.

• GLKS Potato Database
• Centro Internacional de la Papa - CIP (International Potato Center)
• World Potato Congress
• The European Cultivated Potato Database
• British Potato Council
• Online Potato Pedigree Database for cultivated varieties
• The Potato Museum
• Potato Information & Exchange
• [http://www.organicfacts.net/organic-vegetables/organic-potato/organic-control-of-potato-
• [1]

sprouting.html Organic Control of Potato Sprouts]

• GMO Safety: Genetic engineering on potatoes Biological safety research on gm-potatoes

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