Corn, or maize, produces its grain on specialized structures called cobs. The number of harvestable cobs a single plant produces is typically low, generally ranging from one to two fully developed ears under standard agricultural conditions. For most modern hybrid varieties, the goal is not to produce many small ears but to focus the plant’s energy into developing one or two large, high-quality cobs.
The Standard Yield and Biological Limitations
The corn plant is biologically structured to limit its yield to a few large cobs through a process known as apical dominance. This mechanism concentrates the plant’s resources and growth hormones in the main stalk and the highest-developing ear. The main female flowers, which develop into cobs, emerge from the nodes along the stalk, but the plant prioritizes the uppermost one or two ears for full development.
Any potential cobs lower down the stalk are usually suppressed or aborted if resources become scarce, often resulting in small, undeveloped structures called “nubbins.” Modern breeding enhanced this dominance during domestication to maximize the size and consistency of the primary ears.
Male flowers form the tassel at the top, and female flowers, bearing the silks, emerge lower down on the stalk. Each silk strand on a potential cob must be individually pollinated by a grain of pollen from the tassel to produce a single kernel. The plant’s architecture ensures that the pollen dusts down onto the silks, but the process is highly sensitive to environmental stress, which can lead to incomplete kernel fill even on the primary cob.
Key Factors Driving Cob Variation
The genetics of the specific corn variety plays a significant part. Older, open-pollinated types may produce more tillers and ears, while modern hybrid field corn is bred for consistency, often yielding just one large ear per plant.
Environmental stress during the reproductive phase can drastically reduce the number and size of viable cobs. A lack of water, high heat, or nutrient deficiencies—especially during the silking stage—can cause the plant to abort the secondary ears or even fail to fully develop the primary ear. High temperatures, particularly above 90°F, can reduce pollen viability, leading to incomplete pollination and cobs with missing kernels.
The density at which the corn is planted also drives variation in cob size and number. Planting too many plants per acre increases competition for light, water, and nutrients, which forces the plant to allocate fewer resources to each individual ear. Under very dense conditions, plants may only produce one small cob, whereas wider spacing can sometimes allow a plant to fully develop two high-quality ears. Under severe stress, the optimal planting population may be significantly lower to ensure individual plants have adequate resources.
Promoting Optimal Cob Development
Consistent water supply is particularly important during the silking stage, as water stress can dry out the silks, preventing successful pollination. Since corn is a relatively shallow-rooted crop, a thorough soaking of the soil is often needed during dry periods.
Fertilization provides the necessary building blocks for strong growth and cob formation. Nitrogen is particularly important for plant growth, and a deficiency can result in shorter cobs with a reduced number of kernels. Boron is another nutrient that affects grain set, as it is involved in pollen tube growth.
Ensuring complete pollination is also a management focus, particularly for gardeners who may not have large blocks of corn to rely on wind-driven pollen. Planting corn in a square block rather than a long single row increases the chances of pollen reaching the silks, as the majority of pollen comes from neighboring plants. Growers can manually assist this process by gently shaking the tassels to dislodge pollen, which mimics the effect of the wind.