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Tobacco is a tall, herbaceous plant the leaves of which are harvested, cured, and rolled into cigars, shredded for use in cigarettes and pipes, and processed for chewing or snuff. Tobacco is an important crop in almost all tropical countries as well as in many temperate ones. The main source of commercial tobacco is Nicotiana tabacum, although Nicotiana rustica is also grown and is used in Oriental tobaccos. Tobacco has developed a wide range of morphologically different types, from the small-leaved aromatic tobaccos to the large, broad-leaved cigar tobaccos. The most practical means of classifying them is by the method used for curing or drying the leaf.

Tobacco is native to the Americas, and the practice of inhaling the smoke of the dried plant material was first documented in the Mayan culture more than 2,000 years ago. The Mayans moved northward from Central America through the Aztec Empire and eventually took their customs to North American Indian tribes. The Arawak Indians of the Caribbean smoked tobacco; Christopher Columbus, during his 1492 voyage, found them smoking loosely rolled cigars. The Spanish took tobacco seeds to Europe, where Jean Nicot gave the plant its generic name, Nicotiana. Sir Walter Raleigh began the popularization of pipe smoking in Great Britain in 1586, and the cultivation and consumption of tobacco spread with each voyage of discovery from Europe.

Two kinds of tobacco were traded between Europe and America: Spanish, from the West Indies and South America, and Virginia, from what is now the state of Virginia. The Spaniards were the first Europeans to cultivate substantial amounts of tobacco. Despite its popularity in England, James I—who vehemently disapproved of tobacco—forbade its production there.

Europeans at first smoked their tobacco in PIPES, and later in cigars. Cigarettes spread in popularity only after the Crimean War (1854-56); their spread was aided by the development in the United States of the first cigarette-making machine in 1881.

Unlike most other annual agricultural crops, tobacco has a small seed (1 oz = 300,000 seeds), which cannot be sown directly in the field. Seedlings are raised in carefully selected and tended seedbeds where protection is given against heavy rain and excess sun, and great care is taken to ensure the production of healthy, well-nurtured seedlings 6 to 8 weeks after sowing. Young seedlings are planted by hand or mechanical transplanter, and spacing between seedlings and rows varies with the kind of tobacco and with the location.

The crop can tolerate both high rainfall and drought as long as the soil is moist. The best quality tobacco comes from areas where rainfall is evenly distributed throughout the growing season and where a significant diurnal temperature pattern exists. Tobacco needs a minimum of 120 frost-free days and can be grown in a variety of soils.

Most tobacco demands nutrients in addition to those present in the soil. Different types of tobacco need different levels of nitrogen, and all tobaccos need phosphorus and potassium. Minor elements like magnesium and boron are essential; an excess of chlorine leads to loss of color and poor combustion qualities in a cured leaf.

Producing disease-resistant tobacco of acceptable quality is difficult. In the field, as in the seedbed, tobacco is susceptible to many insects, fungal diseases, viruses, and nematodes. The cheapest control is crop rotation or the development of tobaccos with specific resistance to one or more disorders. Only in the United States have breeds been developed that are attractive to both the farmer and the manufacturer. Chemical control is now widely practiced, although the choice of chemicals is constrained by the need to ensure that they do not taint the cured leaf or produce toxic substances when the tobacco is smoked.

Toward the end of the growing period the flower and a number of upper leaves are removed to encourage the growth of the remaining leaves.

Ripe leaf is usually removed by hand from the stalk, two or three leaves per harvest. In the United States and Canada tobacco is often stalk-cut by machine, but in many parts of the world it is still harvested leaf by leaf. To ensure desired smoking characteristics, only fully ripe leaf is used. If unripe leaves are harvested, their quality cannot be improved during the curing process. Although mechanical harvesters have been developed in the United States, most of the world's tobacco is still harvested by hand. Mechanical harvesters are expensive and effective only on large, evenly grown fields. After harvesting, leaves are tied together in pairs on curing sticks or strings.

Used mainly in the manufacture of cigarettes, flue-cured tobacco is lemon, orange, or mahogany in color, with a high sugar content and a medium-to-high nicotine content. Flue curing requires a closed building equipped with a system of ventilation and a source of heat. When heat and humidity are controlled, leaf color changes, moisture is quickly removed, and the leaf and stems dry.

This group includes the original air-cured tobaccos of South and Central America, the cigar tobaccos (subdivided into wrappers, binders, and fillers, depending on their use), and the burley tobaccos, an important component of American cigarettes. These have a low sugar content but vary in nicotine content. Air curing requires an open framework in which sticks of leaves (or whole plants) are hung, protected from wind and sun. Leaf color changes from green to yellow, moisture is removed, and leaves and stems dry slowly.

Fire-cured tobacco, generally dark brown, is used mostly for pipe tobacco mixtures, snuff, and chewing tobacco and has a low sugar but high nicotine content. Fire curing employs an enclosed barn similar to that used for flue curing. Small fires are built on the floor, and the leaves cure in a smoke-laden atmosphere. Whereas flue curing takes 6 to 8 days, fire curing, using far lower temperatures, may take up to 4 weeks.

Sun curing is the drying of uncovered sticks or strings of leaf in the sun. Of all sun-cured tobaccos, the best known are the so-called oriental tobaccos of Turkey, Greece, Yugoslavia, and nearby countries. These are used in cigarettes and have characteristic aromas. They are low in both sugar and nicotine.

After curing, tobacco is separated by quality, which is determined by leaf position on the stalk, leaf color, and number of blemishes. After its sale, the moisture content is standardized (the process is called redrying) to maintain the characteristics of the tobacco for the 12 to 18 months it is held prior to being used. (Oriental tobaccos are not redried; instead, they are stored in small bales and allowed to ferment.) Before this operation it is often threshed to separate the leaf tissue from the stem. After redrying, all tobaccos except oriental are packed into wooden hogsheads, wood or cardboard cases, or bales. In storage, tobacco must be protected against deterioration and insects. After storage, moisture is added and tobacco is blended to achieve the differing qualities needed for cigarettes, cigars, pipe tobaccos, or snuff.

In the mid 1980s, the leading tobacco producers were China (with almost double the crop of the United States, the next largest producer), India, Brazil, the USSR, and Turkey.

Some 180,000 farms in six southern states grow tobacco, often as the only crop. In many hundreds of small towns, it provides the farmer with the sole source of cash to buy equipment and supplies from his local merchants. For many years, it has been an important export crop.

Fears of the health effects of long-term use of tobacco have cut per capita cigarette consumption in the United States by almost 20 percent in the past two decades.

The cigarette industry continues to deny that there is a direct connection between the ingestion of tobacco smoke and the development of respiratory diseases. Although there have been several suits, claims of injury caused by cigarette consumption have not yet been accepted in a court of law. Despite antismoking campaigns and health warnings on cigarette packets, there are still about 55 million U.S. smokers.