Cotton (Gossypium) is a major global fiber crop, providing the natural material for countless products worldwide. Its journey from a single seed to a harvestable commodity is a complex biological process. The life cycle, typically spanning 160 to 180 days, is divided into distinct phases where the plant transitions energy from establishing a sturdy structure to producing the fiber.
Planting and Early Establishment
The life cycle begins with planting the seed into a prepared seedbed. Successful germination requires the soil temperature at planting depth to be at least 60°F or higher to activate metabolic pathways efficiently. Planting depth is typically shallow, ranging from 0.5 to 1.5 inches, which facilitates rapid emergence.
The seed absorbs moisture (imbibition), and the radicle root emerges within two to three days. Emergence generally occurs within four to fourteen days, depending on environmental conditions. Once above ground, the cotyledons (seed leaves) unfold to begin photosynthesis, providing initial energy until the first true leaves develop. This early phase is sensitive to environmental stress, as cold temperatures or excessive soil moisture can hinder the establishment of a healthy stand.
Vegetative Growth
Following seedling establishment, the plant focuses on developing its structural foundation. The main stem grows in a monopodial (straight-growing) pattern, adding new nodes roughly every three days. A deep taproot system is established, often reaching a depth of ten inches by the time the first true leaves appear.
The plant develops two types of branches: vegetative and fruiting. Vegetative branches do not bear fruit and increase the plant’s overall photosynthetic capacity. The accumulation of biomass and leaf area during this time is an investment in future energy production before the plant transitions its focus to fruit production.
Reproductive Development (Squaring and Flowering)
The shift to reproductive growth is marked by the formation of sympodial (zigzag) fruiting branches, typically beginning around the fifth to seventh main-stem node. The first visible sign of reproduction is “squaring,” the formation of the small, triangular flower bud enclosed by three protective bracts. This square develops for 21 to 25 days before opening into a flower.
The flower, which contains both male and female organs, opens in the early morning and is creamy-white on the first day. Pollination, often self-pollination, occurs within a few hours. After fertilization, the petals turn pink or red on the second day before dropping off. This leaves behind the newly forming fruit, known as the cotton boll. The boll is a protective capsule housing the developing seeds and the lint fibers, which grow directly from the seed coat.
Maturation and Boll Opening
The cotton boll requires 50 to 60 days to mature after the flower drops. The period is divided into three phases: enlargement, filling, and maturation.
Enlargement and Filling
During the enlargement phase, the fibers rapidly elongate, forming a thin-walled tubular structure. The filling phase follows, where the secondary walls of the fiber form (deposition), adding thickness and strength to the fiber.
Final Maturation
The final maturation phase involves the drying of the boll wall and dehiscence, where the boll naturally splits open. This reveals the fluffy white cotton lint, which is ready for harvest. To ensure a uniform and clean harvest, growers commonly apply chemical harvest aids like defoliants (to cause leaves to drop) or desiccants (to dry the plant). This practice reduces leaf trash and potential staining, preserving quality.
Harvesting the Crop
Harvesting is timed when a high percentage of bolls, often 60% or more, are open and the fiber is dry. The two primary methods for mechanical collection are the cotton picker and the cotton stripper.
Mechanical Collection Methods
Cotton pickers use rotating spindles to gently twist the lint from the opened boll, leaving the plant stalk relatively intact. Cotton strippers use rollers and brushes to remove the entire boll (both open and unopened) and are often used in regions with shorter growing seasons.
After collection, the harvested seed cotton is compressed into large, dense forms called modules or round bales directly in the field. These modules are covered with tarps and stored temporarily before being transported to the gin, marking the end of the field-based life cycle.