The cotton plant is a warm-season woody perennial shrub, which is grown as an annual field crop. Because the plants are grown in various environments, cotton farmers can choose from many varieties of cotton that are bred to be productive in various environmental and cultural conditions. After the seeds are planted and the plants begin to grow and develop, they must be protected from insects, diseases and weeds.
After the plant flowers, the cotton fibers (lint) develop on the seed in the boll in three stages. In the “elongation” stage (0 to 27 days), the fiber cell develops a thin, expandable primary wall surrounding a large vacuole, and the cell elongates dramatically. During the “thickening” stage (15 to 55 days), the living protoplast shrinks, while a secondary wall composed almost entirely of cellulose is deposited inside the primary wall. By the “maturation” stage, the secondary wall fills most of the fiber cell volume, leaving a small central cavity (the lumen) containing the cytoplasm and the vacuole. As the boll opens, the fiber cells rapidly desiccate, collapse and die. As the tubular cells collapse, they assume a flat, ribbon-like form with twists, called “convolutions.”
Before harvesting, the plants are defoliated to prevent foliage from interfering with mechanical harvesting. Approximately 85% of the total U.S. crop is machine picked and the remaining 15%, primarily from Texas and Oklahoma, is machine stripped. Machine pickers harvest cotton from open bolls, leaving unopened and empty bolls on the plant. This is accomplished with revolving spindles which pluck the fiber out of the boll. Machine strippers strip the entire plant of opened and unopened bolls. The fiber removed from the plant also contains the cottonseeds and is referred to as “seed cotton.” The harvested seed cotton is transported to the gin.