The tobacco plant is a coarse, large-leaved perennial, usually cultivated as an annual, grown from seed in cold frames or hotbeds and then transplanted to the field. Tobacco requires a warm climate and rich, well-drained soil. The plant is susceptible to numerous bacterial, fungal, and viral diseases (e.g., the tobacco mosaic virus) and is attacked by several species of worms, beetles, and moths. The characteristics of many of the named grades depend upon the regional environmental conditions and cultivation techniques. Tobacco leaves are picked as they mature, or they are harvested together with the stalk.
Tobacco leaves are cured, fermented, and aged to develop aroma and reduce the harsh, rank odor and taste of fresh leaves. Fire-curing, dating from pre-Columbian times, is done by drying the leaves in smoke; in air-curing, the leaves are hung in well-ventilated structures; in flue-curing, used for over half the total crop, the leaves are dried by radiant heat from flues or pipes connected to a furnace. The cured tobacco is graded, bunched, and stacked in piles called bulks or in closed containers for active fermentation and aging. Most commercial tobaccos are blends of several types, and flavorings (e.g., maple and other sugars) are often added.