The tomato is an herbaceous, usually sprawling plant in the Solanaceae or nightshade family that is typically cultivated for harvesting its fruit for human consumption. Savory in flavor (and accordingly termed a vegetable; see section Fruit or vegetable below), the fruit of most varieties ripen to a distinctive red color.
The tomato is native to South America. Genetic evidence shows that the progenitors of tomatoes were herbaceous green plants with small green fruit with a center of diversity in the highlands of Peru. These early Solanums diversified into the dozen or so species of tomato recognized today. One species, Solanum lycopersicum, were transported to Mexico, where it was grown and consumed by prehistoric humans. The exact date of domestication is not known. Evidence supports the theory that the first domesticated tomato was a little yellow fruit, ancestor of L. cerasiforme, grown by the Aztecs of Central Mexico who called it xitomatl, meaning plump thing with a navel, and later called tomatl by other Mesoamerican peoples. Aztec writings mention tomatoes were prepared with peppers, corn and salt, likely to be the original salsa recipe.
Aztecs and other peoples in the region used the fruit in their cooking; it was being cultivated in southern Mexico and probably other areas by 500BC. It is thought that the Pueblo people 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 vegetable, originated and was encouraged in Mesoamerica.
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 5mm in diameter, through cherry tomatoes, about the same 1–2 centimetres (0.4–0.8 in) size as the wild tomato, up to “beefsteak” tomatoes 10 centimetres (4 in) or more in diameter. The most widely grown commercial tomatoes tend to be in the 5–6 centimetres (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. Multicolored and striped fruit can also be quite striking. Tomatoes grown for canning and sauces are often elongated, 7–9 centimetres (3–4 in) long and 4–5 centimetres (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, where a 120-acre Morning Star cannery handles 1.2 million pounds of tomatoes an hour during the harvest season where the fields yield about 40 tons to the acre.
Tomatoes are one of the most common garden fruits in the United States and, along with zucchini, have a reputation for outproducing the needs of the grower.
As in most sectors of agriculture, there is increasing demand in developed countries for organic tomatoes, as well as heirloom tomatoes, to make up for flavor and texture faults in commercial tomatoes. Quite a few seed merchants and banks provide a large selection of heirloom seeds. Tomato seeds are occasionally organically produced as well, but only a small percentage of the organic crop area is grown with organic seed. The definition of an heirloom tomato is vague, but unlike commercial hybrids, all are self-pollinators who have bred true for 40 years or more.
There are many (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 flavorful crops at the cost of disease resistance, and productivity. 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.
A variety of heirloom tomatoes
Tomato varieties are roughly divided into several categories, based mostly on shape and size. “Slicing” or “globe” tomatoes are the usual tomatoes of commerce; beefsteaks are large tomatoes often used for sandwiches and similar applications – their kidney-bean shape makes commercial use impractical along with a thinner skin and being not bred for a long shelf life; globe tomatoes are in the category of canners used for a wide variety of processing and fresh eating; 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 solid content for use in tomato sauce and paste and are usually oblong; pear tomatoes are obviously pear shaped and 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; and grape tomatoes which are a more recent introduction are smaller and oblong 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 tomato.
Early tomatoes and cool-summer tomatoes fruit even where nights are cool, which usually discourages fruit set. There are also varieties high in beta carotenes and vitamin A, as hollow tomatoes and tomatoes which 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 “semi-determinate”; 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.
A variety of specific cultivars, including Brandywine (biggest red), Black Krim (lower left corner), Green Zebra (top right), et cetera.
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 tomato cultivars – especially heirlooms – produce fruit in colors other than red, including yellow, orange, pink, black, brown, ivory, white, and purple, though such fruit is not widely available in grocery stores, nor are their seedlings available in typical nurseries, but must be bought as seed, often via mail-order. Less common variations include fruit with stripes (Green Zebra), fuzzy skin on the fruit (Fuzzy Peach, Red Boar), multiple colors (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 flavor to the exclusion of all other qualities, while commercial cultivars are bred for such factors as consistent size and shape, disease and pest resistance, and suitability for mechanized picking and shipping, as well as their ability to be picked before fully ripening. The most commonly home-grown tomato is the Beefsteak variety.
Tomatoes grow well with 7 hours of sunlight a day. A fertilizer with the ratio 5-10-10, often sold as tomato fertilizer or vegetable fertilizer can be used for extra growth and production.
Though it is botanically a berry, a subset of fruit, the tomato is nutritionally categorized as a vegetable (see below). Since “vegetable” is not a botanical term, there is no contradiction in a plant part being a fruit botanically while still being considered a vegetable.
Tomatoes are used extensively in Mediterranean cuisine, especially Italian and Middle Eastern cuisines. The tomato is acidic; this acidity makes easier to preserve tomatoes in home canning whole, in pieces, as tomato sauce, or paste. Tomato juice is often canned and sold as a beverage; Unripe green tomatoes can also be breaded and fried, used to make salsa, or pickled. The fruit is also preserved by drying, often by the sun, and sold either in bags or in jars in oil.
Botanically, a tomato is the ovary, together with its seeds, of a flowering plant: therefore, it is a fruit. However, the tomato is not as sweet as those foodstuffs usually called fruits and, from a culinary standpoint, it is typically served as part of a salad or main course of a meal, as are vegetables, rather than at dessert in the case of most fruits. As noted above, the term vegetable has no botanical meaning and is purely a culinary term. Originally the controversy was that tomatoes are treated as a fruit in home canning practices. Tomatoes are acidic enough to be processed in a water bath rather than a pressure cooker as “vegetables” require.
Roma Tomato or Roma (the “Roma VF” variant is more common in seed catalogs as of 2007) is a plum tomato which is commonly found in supermarkets. The tomato is a meaty, egg- or pear-shaped tomato that is available in red and yellow. It has few seeds and is a good canning and sauce tomato. While Roma is an open-pollinated variety, it is generally not considered an heirloom tomato.
Roma tomatoes are grown in the United States, Mexico, Australia and Great Britain. The vines are determinate and fruit heavily, making Roma a popular variety with gardeners who do a lot of home canning. While Roma is an open-pollinated variety rather than a hybrid, it has been steadily improved to the point where most Roma tomato vines are fusarium wilt and verticillium resistant (thus the VF in the name). Most commercial plum tomatoes sold in markets in the Western Hemisphere are from Roma or related types. Smaller plum-shaped tomatoes are sometimes sold as “baby Romas”.
A smaller-fruited relative known as “Windowbox Roma” is sold as a tomato suitable for window gardens and hanging containers.