The word “tomato” may refer to the plant (Solanum lycopersicum) or the edible, typically red, fruit that it bears. Having originated in America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler climates.
The tomato is consumed in diverse ways, including raw, as an ingredient in many dishes and sauces, and in drinks. While it is botanically a fruit, it is considered a vegetable for culinary purposes (as well as by the United States Supreme Court, seeNix v. Hedden), which has caused some confusion. The fruit is rich in lycopene, which may have beneficial health effects.
The tomato belongs to the nightshade family. The plants typically grow to 1–3 meters (3–10 ft) in height and have a weak stem that often sprawls over the ground and vines over other plants. It is a perennial in its native habitat, although often grown outdoors in temperate climates as an annual.
There are around 7500 tomato varieties grown for various purposes. Heirloom tomatoes are becoming increasingly popular, particularly among home gardeners and organic producers, since they tend to produce more interesting and flavourful crops at the cost of disease resistance and productivity In 1973, Israeli scientists developed the world’s first long shelf-life commercial tomato varieties.
Hybrid plants remain common, since they tend to be heavier producers, and sometimes combine unusual characteristics of heirloom tomatoes with the ruggedness of conventional commercial tomatoes.
Various heirloom tomato cultivars
Tomato varieties are roughly divided into several categories, based mostly on shape and size.
- “Slicing” or “globe” tomatoes are the usual tomatoes of commerce, used for a wide variety of processing and fresh eating.
- Beefsteak tomatoes are large tomatoes often used for sandwiches and similar applications. Their kidney-bean shape, thinner skin, and shorter shelf life makes commercial use impractical.
- Oxheart tomatoes can range in size up to beefsteaks, and are shaped like large strawberries.
- Plum tomatoes, or paste tomatoes (including pear tomatoes), are bred with a higher solids content for use in tomato sauce andpaste, and are usually oblong.
- Pear tomatoes are obviously pear-shaped, and are based upon the San Marzano types for a richer gourmet paste.
- Cherry tomatoes are small and round, often sweet tomatoes generally eaten whole in salads.
- Grape tomatoes, a more recent introduction, are smaller and oblong, a variation on plum tomatoes, and used in salads.
- Campari tomatoes are also sweet and noted for their juiciness, low acidity, and lack of mealiness. They are bigger than cherry tomatoes, but are smaller than plum tomatoes.
Early tomatoes and cool-summer tomatoes bear fruit even where nights are cool, which usually discourages fruit set. There are also varieties high in beta carotenes and vitamin A, hollow tomatoes and tomatoes that keep for months in storage.
Tomatoes are also commonly classified as determinate or indeterminate. Determinate, or bush, types bear a full crop all at once and top off at a specific height; they are often good choices for container growing. Determinate types are preferred by commercial growers who wish to harvest a whole field at one time, or home growers interested in canning. Indeterminate varieties develop into vines that never top off and continue producing until killed by frost. They are preferred by home growers and local-market farmers who want ripe fruit throughout the season. As an intermediate form, there are plants sometimes known as vigorous determinate or semideterminate; these top off like determinates, but produce a second crop after the initial crop. The majority of heirloom tomatoes are indeterminate, although some determinate heirlooms exist.
Most modern tomato cultivars are smooth surfaced, but some older tomato cultivars and most modern beefsteaks often show pronounced ribbing, a feature that may have been common to virtually all pre-Columbian cultivars. While virtually all commercial tomato varieties are red, some cultivars – especially heirlooms – produce fruit in other colours, including green, yellow, orange, pink, black, brown, ivory, white, and purple. Such fruits are not widely available in grocery stores, nor are their seedlings available in typical nurseries, but they can be bought as seed. Less common variations include fruit with stripes (Green Zebra), fuzzy skin on the fruit (Fuzzy Peach, Red Boar), multiple colours (Hillbilly, Burracker’s Favorite, Lucky Cross), etc.
There is also a considerable gap between commercial and home-gardener cultivars; home cultivars are often bred for flavour to the exclusion of all other qualities, while commercial cultivars are bred for such factors as consistent size and shape, disease and pest resistance, suitability for mechanized picking and shipping, and ability to be picked before fully ripening
Tomatoes grow well with seven hours of sunlight a day. A fertilizer with an NPK ratio of 5-10-10 is often sold as tomato fertilizer or vegetable fertilizer, although manure and compost are also used.
Diseases and pests
Tomato cultivars vary widely in their resistance to disease. Modern hybrids focus on improving disease resistance over the heirloom plants. One common tomato disease is tobacco mosaic virus, so smoking or use of tobacco products are discouraged around tomatoes, although there is some scientific debate over whether the virus could possibly survive being burned and converted into smoke. Various forms of mildew and blight are also common tomato afflictions, which is why tomato cultivars are often marked with a combination of letters that refer to specific disease resistance. The most common letters are: V – verticillium wilt, F – fusarium wilt strain I, FF – fusarium wilt strain I and II, N – nematodes, T – tobacco mosaic virus, and A – alternaria.
Another particularly dreaded disease is curly top, carried by the beet leafhopper, which interrupts the lifecycle, ruining a nightshade plant as a crop. As the name implies, it has the symptom of making the top leaves of the plant wrinkle up and grow abnormally.
Some common tomato pests are stink bugs, cutworms, tomato hornworms and tobacco hornworms, aphids, cabbage loopers,whiteflies, tomato fruitworms, flea beetles, red spider mite, slugs, and Colourado potato beetles.
Tomato plants produce the plant peptide hormone systemin after an insect attack. Systemin activates defensive mechanisms, such as the production of protease inhibitors to slow the growth of insects. The hormone was first identified in tomatoes, but similar proteins have been identified in other species since.
Tomatoes serve, or are served by, a large variety of companion plants.
In fact, one of the most famous pairings is the tomato plant and carrots; studies supporting this relationship having produced a popular book about companion planting,Carrots Love Tomatoes Additionally, the devastating tomato hornworm has a major predator in various parasitic wasps, whose larvae devour the hornworm, but whose adult form drinks nectar from tiny-flowered plants like umbellifers. Several species of umbellifer are therefore often grown with tomato plants, including parsley, queen anne’s lace, and occasionally dill. These also attract predatory flies that attack various tomato pests ]
On the other hand, borage is thought to actually repel the tomato hornworm moth.
Other plants with strong scents, like alliums (onions, chives, garlic) and mints (basil, oregano, spearmint) are simply thought to mask the scent of the tomato plant, making it harder for pests to locate it, or to provide an alternative landing point, reducing the odds of the pests from attacking the correct plant. These plants may also subtly impact the flavour of tomato fruit. Ground cover plants, including mints, also stabilize moisture loss around tomato plants and other solaneae, which come from very humid climates, and therefore may prevent moisture-related problems like blossom end rot.
Finally, tap-root plants like dandelions break up dense soil and bring nutrients from down below a tomato plant’s reach, possibly benefiting their companion.
Tomato plants, on the other hand, protect asparagus from asparagus beetles, because they contain solanum that kills this pest, while asparagus plants (as well as marigolds) contain a chemical that repels root nematodes known to attack tomato plants.
In the wild, original state, tomatoes required cross-pollination; they were much more self-incompatible than domestic cultivars. As a floral device to reduce selfing, the pistil of wild tomatoes extends farther out of the flower than today’s cultivars. The stamens were, and remain, entirely within the closed corolla.
As tomatoes were moved from their native areas, their traditional pollinators, (probably a species of halictid bee) did not move with them. The trait of self-fertility became an advantage, and domestic cultivars of tomato have been selected to maximize this trait.
This is not the same as self-pollination, despite the common claim that tomatoes do so. That tomatoes pollinate themselves poorly without outside aid is clearly shown in greenhouse situations, where pollination must be aided by artificial wind, vibration of the plants (one brand of vibrator is a wand called an “electric bee” that is used manually), or more often today, by culturedbumblebees. The anther of a tomato flower is shaped like a hollow tube, with the pollen produced within the structure, rather than on the surface, as in most species. The pollen moves through pores in the anther, but very little pollen is shed without some kind of outside motion. The best source of outside motion is a sonicating bee, such as a bumblebee, or the original wild halictid pollinator. In an outside setting, wind or animals provide sufficient motion to produce commercially viable crops.
Hydroponic and greenhouse cultivation
Tomatoes are often grown in greenhouses in cooler climates, and there are cultivars such as the British ‘Moneymaker’ and a number of cultivars grown in Siberia that are specifically bred for indoor growing. In more temperate climates, it is not uncommon to start seeds in greenhouses during the late winter for future transplant.
Greenhouse tomato production in large-acreage commercial greenhouses and owner-operator stand-alone or multiple-bay greenhouses is on the increase, providing fruit during those times of the year when field-grown fruit is not readily available. Smaller sized fruit (cherry and grape), or cluster tomatoes (fruit-on-the-vine) are the fruit of choice for the large commercial greenhouse operators while the beefsteak varieties are the choice of owner-operator growers.
Hydroponic tomatoes are also available, and the technique is often used in hostile growing environments, as well as high-density plantings.
Picking and ripening
Tomatoes are often picked unripe (and thus coloured green) and ripened in storage with ethylene. Unripe tomatoes are firm. As they ripen they soften until reaching the ripe state where they are red or orange in colour and slightly soft to the touch. Ethylene is a hydrocarbon gas produced by many fruits that acts as the molecular cue to begin the ripening process. Tomatoes ripened in this way tend to keep longer, but have poorer flavour and a mealier, starchier texture than tomatoes ripened on the plant. They may be recognized by their colour, which is more pink or orange than the other ripe tomatoes’ deep red, depending on variety.
A machine-harvestable variety of tomato (the “square tomato”) was developed in the 1950s by University of California, Davis’s Gordie C. Hanna, which, in combination with the development of a suitable harvester, revolutionized the tomato-growing industry. In 1994, Calgene introduced a genetically modified tomato called the ‘FlavrSavr’, which could be vine ripened without compromising shelf life. However, the product was not commercially successful, and was sold only until 1997.
Recently, stores have begun selling “tomatoes on the vine”, which are determinate varieties that are ripened or harvested with the fruits still connected to a piece of vine. These tend to have more flavour than artificially ripened tomatoes (at a price premium).
Slow-ripening cultivars of tomato have been developed by crossing a nonripening cultivar with ordinary cultivars. Cultivars were selected whose fruits have a long shelf life and at least reasonable flavour.
At home, fully ripe tomatoes can be stored in the refrigerator, but are best kept at room temperature. Tomatoes stored cold will still be edible, but tend to lose flavour] thus, “Never Refrigerate” stickers are sometimes placed on tomatoes in supermarkets.
Tomatoes that have been modified using genetic engineering have been developed, and although none are commercially available now, they have been in the past. The first commercially available genetically modified food was a variety of tomato named (the Flavr Savr), which was engineered to have a longer shelf life[ Scientists are continuing to develop tomatoes with new traits not found in natural crops, such as increased resistance to pests or environmental stresses. Other projects aim to enrich tomatoes with substances that may offer health benefits or provide better nutrition.
The tomato is now grown and eaten around the world. It is used in diverse ways, including raw in salads, and processed into ketchup or tomato soup. Unripe green tomatoes can also be breaded and fried, used to make salsa, or pickled. Tomato juice is sold as a drink, and is used in cocktails such as the Bloody Mary.
Tomatoes are acidic, making them especially easy to preserve in home canning whole, in pieces, as tomato sauce or paste. The fruit is also preserved by drying, often in the sun, and sold either in bags or in jars with oil.
Tomatoes are used extensively in Mediterranean cuisine. They are a key ingredient in pizza, and are commonly used in pasta sauces. They are also used in gazpacho(Spanish cuisine) and pa amb tomàquet (Catalan cuisine).
Though it is botanically a berry, a subset of fruit, the tomato is a vegetable for culinary purposes, because of its savory flavour (see below).
Tomatoes are now eaten freely throughout the world, and their consumption is believed] to benefit the heart, among other organs. They contain the carotene lycopene, one of the most powerful natural antioxidants. In some studies, lycopene, especially in cooked tomatoes, has been found to help prevent prostate cancer,but other research contradicts this claim Lycopene has also been shown to improve the skin’s ability to protect against harmful UV rays,[ A study done by researchers at Manchester and Newcastle universities revealed that tomato can protect against sunburn and help keeping the skin looking youthful.] Natural genetic variation in tomatoes and their wild relatives has given a genetic plethora of genes that produce lycopene, carotene, anthocyanin, and other antioxidants. Tomato varieties are available with double the normal vitamin C(Doublerich), 40 times normal vitamin A (97L97), high levels of anthocyanin (resulting in blue tomatoes), and two to four times the normal amount of lycopene (numerous available cultivars with the high crimson gene).
Lycopene has also been shown to protect against oxidative damage in many epidemiological and experimental studies. In addition to its antioxidant activity, other metabolic effects of lycopene have also been demonstrated. The richest source of lycopene in the diet is tomato and tomato derived products. Tomato consumption has been associated with decreased risk of breast cancer, head and neck cancers and might be strongly protective against neurodegenerative diseases. Tomatoes, tomato sauces and puree are said to help lower urinary tract symptoms (BPH) and may have anticancer properties. Tomato consumption might be beneficial for reducing cardiovascular risk associated with type 2 diabetes.
Tomatoes that are not yet ripe are optimally stored at room temperature uncovered, out of direct sunlight, until ripe. In this environment, they have a shelf life of three to four days. When ripe, they should be used in one to two days. Tomatoes should only be refrigerated when well ripened, but this will affect flavour.
Leaves, stems, and green unripe fruit of the tomato plant contain small amounts of the toxic alkaloid tomatine They also contain solanine, a toxic alkaloid found in potato leaves and other plants in the nightshade family. Use of tomato leaves in tea (tisane) has been responsible for at least one death. However, levels of tomatine in foliage and green fruit are generally too small to be dangerous unless large amounts are consumed, for example, as greens. Small amounts of tomato foliage are sometimes used for flavouring without ill effect, and the green fruit is sometimes used for cooking, particularly as fried green tomatoes. Compared to potatoes the amount of solanine in green or ripe tomatoes is low; however, even in the case of potatoes while solanine poisoning resulting from dosages several times normal human consumption has been demonstrated, actual cases of poisoning resulting from excessive consumption of potatoes that have high concentration of solanine are rare.
Tomato plants can be toxic to dogs if they eat large amounts of the fruit, or chew plant material.
Aztecs and other peoples in Mesoamerica used the fruit in their cooking. The exact date of domestication is unknown: by 500 BCE, it was already being cultivated in southern Mexico and probably other areas. The Pueblo people are thought to have believed that those who witnessed the ingestion of tomato seeds were blessed with powers of divination. The large, lumpy tomato, a mutation from a smoother, smaller fruit, originated in Mesoamerica, and may be the direct ancestor of some modern cultivated tomatoes.
Spanish conquistador Hernán Cortés may have been the first to transfer the small yellow tomato to Europe after he captured the Aztec city of Tenochtítlan, now Mexico City, in 1521, although Christopher Columbus, a Genoese working for the Spanish monarchy, may have taken them back as early as 1493. The earliest discussion of the tomato in European literature appeared in an herbal written in 1544 by Pietro Andrea Mattioli, an Italian physician and botanist, who suggested that a new type of eggplant had been brought to Italy that was blood red or golden colour when mature and could be divided into segments and eaten like an eggplant—that is, cooked and seasoned with salt, black pepper, and oil. However it wasn’t until ten years later that tomatoes were named in print by Mattioli as pomi d’oro, or “golden apple”.
After the Spanish colonization of the Americas, the Spanish distributed the tomato throughout their colonies in the Caribbean. They also took it to the Philippines, from where it spread to southeast Asia and then the entire Asian continent. The Spanish also brought the tomato to Europe. It grew easily in Mediterranean climates, and cultivation began in the 1540s. It was probably eaten shortly after it was introduced, and was certainly being used as food by the early 17th century in Spain. The earliest discovered cookbook with tomato recipes was published in Naples in 1692, though the author had apparently obtained these recipes from Spanish sources. In certain areas of Italy, such as Florence, however, the fruit was used solely as a tabletop decoration before it was incorporated into the local cuisine in the late 17th or early 18th century.
The recorded history of tomatoes in Italy dates back to October 31, 1548 when the house steward of Cosimo de’ Medici, the grand duke of Tuscany, wrote to the Medici private secretary informing him that the basket of tomatoes sent from the grand duke’s Florentine estate at Torre del Gallo “had arrived safely.” Tomatoes were grown mainly as ornamentals early on after their arrival in Italy. For example, the Florentine aristocrat Giovanvettorio Soderini wrote how they “were to be sought only for their beauty” and were grown only in gardens or flower beds. The tomato’s ability to mutate and create new and different varieties helped contribute to its success and spread throughout Italy. However, even in areas where the climate supported growing tomatoes, their proximity of growing to the ground suggested low status. They were not adopted as a staple of the peasant population because they were not as filling as other fruits already available. Additionally, both toxic and inedible varieties discouraged many people from attempting to consume or prepare them.
Tomatoes were not grown in England until the 1590s. One of the earliest cultivators was John Gerard, a barber-surgeon. Gerard’s Herbal, published in 1597, and largely plagiarized from continental sources, is also one of the earliest discussions of the tomato in England. Gerard knew the tomato was eaten in Spain and Italy. Nonetheless, he believed it was poisonous (in fact, the plant and raw fruit do have low levels of tomatine, but are not generally dangerous; see below). Gerard’s views were influential, and the tomato was considered unfit for eating (though not necessarily poisonous) for many years in Britain and its North American colonies. By the mid-18th century, tomatoes were widely eaten in Britain, and before the end of that century, the Encyclopædia Britannica stated the tomato was “in daily use” in soups, broths, and as a garnish.
The tomato was introduced to cultivation in the Middle East/Asia by John Barker, British consul in Aleppo circa 1799 to 1825. Nineteenth century descriptions of its consumption are uniformly as an ingredient in a cooked dish. In 1881, it is described as only eaten in the region “within the last forty years”
The tomato entered Iran through two separate routes; one was through Turkey and Armenia, and the other was through the Qajar royal family’s frequent travels to France. The early name used for tomato in Iran was Armani badenjan (Armenian eggplant). Currently, the name used for tomato in Iran is gojeh farangi [French plum].
The earliest reference to tomatoes being grown in British North America is from 1710, when herbalist William Salmon reported seeing them in what is today South Carolina. They may have been introduced from the Caribbean. By the mid-18th century, they were cultivated on some Carolina plantations, and probably in other parts of the Southeast as well. Possibly, some people continued to think tomatoes were poisonous at this time; and in general, they were grown more as ornamental plants than as food. Thomas Jefferson, who ate tomatoes in Paris, sent some seeds back to America.
Alexander W. Livingston was the first person who succeeded in upgrading the wild tomato, developing different breeds and stabilizing the plants. In the 1937 yearbook of the Federal Department of Agriculture, it was declared that “half of the major varieties were a result of the abilities of the Livingstons to evaluate and perpetuate superior material in the tomato”. Livingston’s first breed of tomato, the Paragon, was introduced in 1870. In 1875, he introduced the Acme, which was said to be involved in the parentage of most of the tomatoes introduced by him and his competitors for the next twenty-five years.
When Alexander W. Livingston had begun his attempts to develop the tomato as a commercial crop, his aim had been to grow tomatoes smooth in contour, uniform in size and having better flavour. One year, after many attempts, he passed through his fields, picking out particular tomato plants having distinct characteristics and heavy foliage. He saved the seeds carefully. The following spring he set two rows across his family garden located just below the hill and milk house. To his happy surprise, each plant bore perfect tomatoes like the parent vine. After five years, the fruit became fleshier and larger. In 1870, Alexander introduced the Paragon and tomato culture began at once to be a great enterprise of the county. Today, the crop is grown in every state in the Union. He eventually developed over seventeen different varieties of the tomato plant.
Because of the long growing season needed for this heat-loving crop, several states in the US Sun Belt became major tomato-producers, particularly Florida and California. In California, tomatoes are grown under irrigation for both the fresh fruit market and for canning and processing. The University of California, Davis (UC Davis) became a major center for research on the tomato. The C.M. Rick Tomato Genetics Resource Center at UC Davis is a gene bank of wild relatives, monogenic mutants and miscellaneous genetic stocks of tomato. The Center is named for the late Dr. Charles M. Rick, a pioneer in tomato genetics research. Research on processing tomatoes is also conducted by the California Tomato Research Institute in Escalon, California.
In California, growers have used a method of cultivation called dry-farming, especially with Early Girl tomatoes. This technique encourages the plant to send roots deep to find existing moisture in soil that retains moisture, such as clayey soil.
Modern commercial varieties
The poor taste and lack of sugar in modern garden and commercial tomato varieties resulted from breeding of tomatoes which ripen uniformly red. This change occurred after discovery of a variety in the mid 20th century which ripened uniformly which was then widely cross-bred to produce attractive red fruit without the typical green ring surrounding the stem on uncross-bred varieties. Prior to general introduction of this trait tomatoes were able to produce more sugar during the process of ripening and were sweeter and more flavourful.
The tomato is now grown worldwide for its edible fruits, with thousands of cultivars having been selected with varying fruit types, and for optimum growth in differing growing conditions. Cultivated tomatoes vary in size, from tomberries, about 5 mm in diameter, through cherry tomatoes, about the same 1–2 centimeters (0.4–0.8 in) size as the wild tomato, up to beefsteak tomatoes 10 centimeters (4 in) or more in diameter. The most widely grown commercial tomatoes tend to be in the 5–6 centimeters (2.0–2.4 in) diameter range. Most cultivars produce red fruit, but a number of cultivars with yellow, orange, pink, purple, green, black, or white fruit are also available. Multicoloured and striped fruit can also be quite striking. Tomatoes grown for canning and sauces are often elongated, 7–9 centimeters (3–4 in) long and 4–5 centimeters (1.6–2.0 in) diameter; they are known as plum tomatoes, and have a lower water content. Roma-type tomatoes are important cultivars in the Sacramento Valley.
Tomatoes are one of the most common garden fruits in the United States and, along with zucchini, have a reputation for out producing the needs of the grower
Quite a few seed merchants and banks provide a large selection of heirloom seeds. The definition of an heirloom tomato is vague, but unlike commercial hybrids, all are self-pollinators that have bred true for 40 years or more.
About 150 million tons of tomatoes were produced in the world in 2009. China, the largest producer, accounted for about one quarter of the global output, followed by United States and India. For one variety, plum or processing tomatoes, California accounts for 90% of U.S. production and 35% of world production.
According to FAOSTAT, the top producers of tomatoes (in tonnes) in 2010 were:
Within the EU, there are several areas that grow tomatoes with Protected Geographical Status. These include:
- Pomodoro di Pachino (PGI), in Sicily
- Pomodoro S. Marzano dell’Agro Sarnese-Nocerino (PDO), in south Italy
- Tomaten von der Insel Reichenau (PGI), from Reichenau Island, Germany
- Pomodorino_del_Piennolo_del_Vesuvio (PDO), in Mt Vesuvius area.
Top Five Tomato Producers – 2010
145,751,507 (11th overall)