Corn, or maize (Zea mays), is a tall, annual grass that has become one of the world’s most widely cultivated cereal grains. As a staple crop, its life cycle is a precisely timed biological process that transforms a single seed into a towering stalk bearing ears of grain. This journey from a dormant kernel to a mature plant is divided into vegetative stages focused on structure and reproductive stages centered on grain production.
The Corn Kernel as the Seed Source
The corn plant originates from the kernel. This kernel contains all the genetic material and stored energy necessary for the initial burst of growth. The main internal components are the embryo, or germ, which is the tiny new plant, and the endosperm, a large region composed primarily of starch that serves as the food supply.
To initiate growth, the dormant kernel must first absorb a significant amount of water. Successful germination requires the soil temperature to be at least 10 degrees Celsius, though an optimal temperature of around 18 degrees Celsius is preferred for rapid emergence. Once water is absorbed, the radicle, the embryonic root, is the first structure to push out of the kernel, anchoring the seedling and beginning nutrient uptake.
Shortly after, the coleoptile, a protective sheath covering the embryonic shoot, emerges and pushes toward the soil surface. This initial growth phase, known as emergence (VE), is entirely dependent on the starch reserves stored within the endosperm. The depth at which the kernel is planted, typically 1.5 to 2 inches, is determined to ensure the coleoptile can reach the light without exhausting its food reserves before photosynthesis can begin.
Building the Plant: Vegetative Growth Stages
Following emergence, the corn plant enters a period of intense structural development known as the vegetative (V) stages, where the focus is on building biomass. The young plant quickly develops two types of root systems: the short-lived seminal roots that arise from the kernel, and the permanent nodal roots that begin to grow from the lower nodes of the stalk. By the time the plant reaches the V3 stage, the nodal root system becomes the primary source for water and nutrient absorption, firmly anchoring the rapidly growing stalk.
The stalk, or culm, is composed of segments separated by distinct joints called nodes, with the spaces between them being the internodes. Leaves unroll from the central whorl, and each fully developed leaf is marked by a visible collar at its base, which is used to stage the plant’s growth numerically (V1, V2, etc.). During this phase, the leaves act as solar panels, converting sunlight into energy through photosynthesis to fuel the massive structural growth of the plant.
New leaves can unfurl every two to four days under ideal conditions during this rapid growth period. Until the V5 or V6 stage, the growing point of the stalk, where new cells are produced, remains below the soil surface, protecting it from minor environmental damage. Once the growing point moves above the ground, the final number of leaves and the structural capacity of the plant are largely determined, setting the stage for the reproductive phase that follows.
Making the Ear: Pollination and Reproduction
The final phase of the corn life cycle begins when the plant transitions from vegetative growth to reproduction, marked by the appearance of the male and female flowering structures. Corn is a monoecious plant, meaning it has separate male and female flowers on the same individual. The male flower, called the tassel, emerges from the very top of the stalk, signifying the VT (Tasseling) stage.
The tassel begins to shed millions of microscopic pollen grains, which are lightweight and dispersed primarily by the wind over a period of about five to eight days. The female flowers are located lower on the stalk, encased within the husks of the developing ear, and are ready for fertilization when the silks emerge. Each silk is a delicate strand connected to a single potential kernel, and successful pollination occurs when a pollen grain lands on a silk, germinates, and sends a tube down to fertilize the ovule.
The reproductive stages (R-stages) are tracked by kernel development, beginning with R1 (Silking), when the silks are visible outside the husks. Once fertilized, the kernels progress through R3, the Milk stage, where they are filled with a white, milky fluid rich in starch and sugars. This is followed by R5, the Dent stage, where a small indentation forms in the crown of the kernel as moisture content decreases. The life cycle concludes at R6, Physiological Maturity, which is visible as a dark layer of cells, or “black layer.” This layer forms where the kernel attaches to the cob, signaling that the grain is finished accumulating dry matter.