The Botany of the Tobacco Plant

Tobacco Plants at Sunset

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There are few activities more controversial than smoking tobacco. Smoking is clearly detrimental to human health, but there is little doubt that tobacco is a highly profitable plant species. Let's learn more about the plant itself, including its history, anatomy and physiology, growth habit plant types, and other potential uses.

History and Background of Tobacco

Nicotiana tabacum is the Latin name for tobacco. It belongs to the plant family Solanaceae, so, perhaps surprisingly, tobacco is botanically related to potatoes, tomatoes, and eggplant!

Tobacco is native to the Americas, and cultivation was thought to have begun as early as 6000 BCE. It is believed that leaf blades were wilted, dried, and rolled to make primitive cigars. Columbus noted Cuban natives smoking cigars when he discovered America, and in 1560, Jean Nicot, the French ambassador to Portugal, brought tobacco to England and France. Nicot made a fortune selling the plant to Europeans. Nicot also reportedly gifted tobacco to the queen of France to cure her headaches. (Did you notice that the Latin genus name for tobacco, Nicotiana, was named after Jean Nicot?)

Anatomy and Physiology

The cultivated tobacco plant normally grows to one or two feet high. The five flower petals are contained within a Corolla and can be colored white, yellow, pink, or red. The tobacco fruit (yes, tobacco bears fruit!) measures at 1.5 - 2 mm, and consists of a capsule containing two seeds.

With the tobacco plant, however, it is the leaves that are the most economically important. The leaf blades are enormous, often growing to 20 inches long and 10 inches wide. The leaf shape can be ovate (egg-shaped), obcordate (heart-shaped) or elliptic (oval, but with a small point at one end). The leaves grow toward the base of the plant, and can be lobed or unlobed but are not separated into leaflets. On the stem, the leaves appear alternately, with one leaf per node along the stem. The leaves possess a distinct petiole. The underside of the leaf is fuzzy or hairy.

Why are the tobacco leaves important? The leaves are the plant part containing the nicotine. However, the nicotine is manufactured in the plant roots, not the leaves! The nicotine is transported to the leaves via the xylem. Some species of Nicotiana are very high in nicotine content; Nicotiana rustica leaves, for example, can contain up to 18% nicotine.

Growing Tobacco Plants

Tobacco, a plant that is cultivated as an annual but is actually a perennial, is propagated by seed. The seeds are sown in beds; one ounce of seed in 100 square yards of soil can produce up to four acres of flue-cured tobacco, or up to three acres of burley tobacco. The plants grow for between six and ten weeks before the seedlings are transplanted into the fields. The plants are topped (their heads are cut off!) before the seed head develops, except for those plants that are used to produce next year's seed. The reason the plant tops are removed when flowering begins is so all the plant's energy goes to increase the size and the thickness of the leaves.

The tobacco suckers (the flowering stalks and branches, which appear in response to the plant being topped) are removed so that only the large leaves are produced on the main stem. Because growers want the leaves to be large and lush, the tobacco plants are fertilized very heavily with nitrogen fertilizer. Cigar-wrapper tobacco, a staple of Connecticut agriculture, is produced under partial shade—resulting in thinner and less damaged leaves.

Plants grow in the field for three to five months until harvest. The leaves are removed and purposely wilted in drying barns, and fermentation takes place during curing.

Tobacco Types

Several types of tobacco are grown, depending on their use:

  • Fire-cured, used for snuff and chewing tobacco.
  • Dark air-cured, used for chewing tobacco.
  • Air-cured (Maryland) tobacco, used for cigarettes.
  • Air-cured cigar tobaccos, used for cigar wrappers and fillers.
  • Flue-cured, used for cigarette, pipe, and chewing tobacco.
  • Burley (air-cured), used for cigarette, pipe, and chewing tobacco.

Fire curing is basically what the name suggests; open fires are used so that the smoke can reach the leaves. The smoke makes the leaves darker colored and more distinctly flavored. No heat is used in air curing except to prevent mold. In flue curing, heat is applied in such a way that no smoke reaches the leaves hung in racks.

Other Potential Uses

What other possibilities are there for tobacco, as smoking rates have been vastly reduced over the last 20 years? Believe it or not, there is a possibility that tobacco oils can be used in biofuels. Also, researchers in India have patented an extract from tobacco called solansole, for use in several drug types.