The cotton plant, a significant source of natural fiber, undergoes a distinct life cycle from a tiny seed to a harvest-ready plant. Understanding each phase of its development is important for appreciating the journey of this versatile crop.
Germination and Emergence
Germination, the initial stage of the cotton plant’s life, requires specific environmental conditions for success. Cotton seeds germinate optimally in warm soil temperatures, ideally between 82°F to 86°F (28°C to 30°C). Adequate moisture and a high concentration of soil oxygen are also important for the seed to sprout. The radicle, the embryonic root, is the first part to emerge from the seed coat, pushing downward to establish the plant’s root system.
Following radicle emergence, the seedling typically breaks through the soil surface within 4 to 9 days after planting. This emergence is marked by the appearance of two seed leaves, known as cotyledons, which unfold above the soil. These cotyledons provide initial nourishment to the young plant through stored energy from the seed and perform some photosynthesis until the true leaves develop. Shortly after, the first true leaves, which resemble the mature plant’s foliage, begin to form, taking over the primary role of photosynthesis.
Vegetative Growth and Squaring
After the seedling emerges, the cotton plant enters a phase of rapid vegetative growth, focusing on building its structure and leaf area. The main stem elongates, developing a series of nodes and internodes, with leaves and branches forming at each node. During this period, the plant establishes a deep taproot system, which can reach depths of 10 inches and acquires water and nutrients from the soil.
Approximately four to five weeks after planting, the plant begins a process called “squaring,” which marks the visible onset of reproductive growth. Squares are small, triangular flower buds that develop in the axils of the leaves on fruiting branches. These fruiting branches typically begin to form at the sixth or seventh node on the main stem. The development of these squares is a precursor to flowering, with each square taking about three weeks to develop into a mature flower.
Flowering and Boll Formation
Flowering, the reproductive phase, begins around 50 to 60 days after planting and can continue for four to six weeks. Cotton flowers are self-pollinating and initially appear as creamy white blooms. Pollination occurs within a few hours of the flower opening. Over the next one to two days, the pollinated flower undergoes a color change, turning pink and then red or dark pink before eventually drying up and falling off the plant.
Once fertilized, the base of the flower develops into a fruit known as a cotton boll. This green, rounded structure is a segmented pod that houses the developing cotton fibers and seeds. Each boll typically contains 32 to 40 seeds, with fibers elongating from the seed coat. The development of the boll involves three main phases: enlargement, where fibers elongate and the boll reaches its maximum size; filling, where secondary cell wall thickening of the fibers occurs; and maturation, where the fibers and seeds fully mature.
Boll Opening and Harvest
The final stage of the cotton plant’s life cycle for fiber production involves the maturation and opening of the bolls, preparing them for harvest. Cotton bolls require approximately 50 to 60 days after flowering to reach maturity and open. As the boll matures, its outer walls dry and split open, a process called dehiscence, revealing the fluffy white cotton lint inside. The lint then dries and expands, making the cotton ready for collection.
Harvesting begins once most of the bolls have opened and the cotton lint is dry. Most cotton in the United States is harvested mechanically. Two primary mechanical methods are used: machine pickers, which use revolving spindles to pull cotton from open bolls, and machine strippers, which remove the entire boll, including some plant material. While mechanical harvesting is efficient for large-scale operations, manual picking allows for selective harvesting of only mature bolls and is still used in some smaller or specialized contexts.