The cotton plant is a shrub belonging to the genus Gossypium within the mallow family Malvaceae. It is the source of one of the world’s most significant natural fibers. The flower is botanically referred to as the cotton flower or a cotton bloom. Confusion often arises because the textile fiber does not come from the petals, but rather from the fruit that develops after the bloom.
The Flowering Stage: Buds and Blooms
The reproductive cycle begins with the formation of the flower bud, which is commonly called a “square.” Cotton growers use this term because of the distinct, somewhat triangular shape of the three small, leaf-like structures, or bracts, that enclose and protect the developing bud. The square develops over approximately three weeks before it matures into a flower ready to open.
Once the square is fully developed, it blooms into a large, five-petaled flower, which resembles a hibiscus, another member of the same plant family. When the flower first opens in the morning, it is typically a creamy white or light yellowish color. The flower’s brief existence is solely dedicated to pollination, which must occur within a very short window of time.
The bloom lasts for only one to two days before it begins to change color. The petals transition from white to a pink or reddish hue as the flower withers. After fertilization takes place, the entire flower structure dries up and drops off the plant, leaving behind the small, fertilized ovary that will swell into the fruit.
The Fruiting Stage: Development of the Cotton Boll
The structure that remains after the flower drops is the fruit, which is known as the cotton boll. This hard, green capsule holds the plant’s seeds and is the source of the harvestable cotton fiber. The boll develops from the fertilized ovary and is segmented internally into three to five compartments called locules, each containing several seeds.
The cotton fiber is not a petal or part of the flower, but rather a mass of elongated single cells growing from the surface of each seed coat. Boll development proceeds through three distinct phases. The first is the enlargement phase, where the fibers rapidly elongate, forming a thin-walled tubular structure over approximately three weeks. This is followed by the filling phase, where the secondary cellulose walls are deposited inside the fiber, building its strength and maturity.
Under optimal conditions, the boll requires about 50 days of growth after the flower drops to reach full maturity. During the final maturation stage, the boll dries and hardens, eventually undergoing dehiscence. The dark, protective outer shell splits open along its sutures, revealing the fluffy white mass of mature cotton fibers, or lint, ready for harvest.