Corn (maize) is an annual crop whose entire life cycle, from seed to harvestable ear, is completed within a single growing season. Its growth is dictated by seasonal weather patterns, requiring warm temperatures and the absence of frost. This reliance on seasonal warmth means development begins in the spring and concludes in the fall. The growing season involves three distinct periods: the planting window, the summer growth phase, and the final harvest.
The Timing of Planting
The corn growing season officially begins in the spring, but the exact planting date is determined by soil conditions rather than a fixed calendar day. Corn seeds require a minimum soil temperature of 50 to 55°F (10 to 13°C) at the planting depth for successful germination and emergence. Planting into colder soil causes the seed to sit dormant, increasing its vulnerability to disease, insects, and seedling death, often due to “imbibitional chilling.”
The planting window is heavily influenced by geography. In the Southern United States, this window may open in late March, while in the Northern Corn Belt, it is typically delayed until late April or early May. Farmers often check the soil temperature early in the morning, around 6 or 7 a.m., to ensure the temperature is consistently above the 50°F threshold, as the soil is coldest at this time.
Once planted, the speed of germination and emergence is temperature-dependent. In cooler soil, between 50 and 55°F, emergence can take up to three weeks, but in warmer soil above 60°F, seedlings can break the surface in as little as ten days. The primary goal during this initial spring period is to establish a healthy stand before the rapid growth of summer begins.
Mid-Season Growth and Development
The mid-season phase, covering the summer months, is characterized by rapid vegetative growth and reproductive development. Corn is a heat-loving crop, thriving in daytime temperatures between 77 and 91°F (25 to 33°C). This period is when the plant builds its structure, accumulating biomass and requiring significant moisture to support its high metabolic rate.
The plant progresses through several vegetative stages before entering the reproductive phase. The most significant biological events occur in mid-summer, specifically tasseling and silking, which are the male and female flowering parts, respectively. Pollination is a delicate process that requires adequate moisture and moderate temperatures, as excessive heat during this time can reduce the number of kernels that develop on the ear.
The entire growing cycle, from planting to physiological maturity, typically lasts between 90 and 150 days, depending on the variety and regional climate. After successful pollination, the plant shifts its energy to kernel development, passing through the blister, milk, and dough stages. By the end of this summer phase, the ear has reached its full size and is beginning to dry down in preparation for the final stage.
Harvesting the Crop
The end of the corn growing season spans late summer through the fall, with the timing determined by the intended use of the crop. Sweet corn, grown for direct human consumption, is harvested early in late summer when the kernels are tender and full of sugar. This harvest occurs at a high moisture content, often between 70% and 75%, during the “milk stage” of kernel development.
Field corn, used primarily for livestock feed, ethanol, and industrial products, requires a much later harvest to allow the grain to dry naturally. This variety is left in the field until it reaches physiological maturity, a point marked by the formation of a “black layer” at the base of the kernel, indicating that nutrient flow from the plant has stopped.
Growers generally harvest field corn when the kernel moisture content drops to 15% to 20% to minimize the need for artificial drying. If the corn is intended for long-term storage, the moisture must be reduced further to 13% to 15% to prevent spoilage and mold. This focus on low moisture content means the field corn harvest often extends into late fall and early winter, concluding the seasonal cycle.