Maize, commonly known as corn, is one of the world’s most important staple crops. Unlike many garden plants that rely on insects, corn depends almost entirely on wind for fertilization. This method requires a unique plant structure and the production of an immense amount of pollen.
The Unique Anatomy of Corn
The corn plant is monoecious, meaning a single plant bears separate male and female reproductive flowers. The male structure is the tassel, a large, branched inflorescence that forms at the very top of the plant, ensuring maximum dispersal by air currents. The tassel is composed of spikelets, each holding anthers that produce and release the fine, yellow pollen grains.
The female flowers are housed lower down on the stalk, forming the ear, which is tightly encased by husks. The silks are the functional part of the female flower, serving as the stigma that receives the pollen. Each silk is an elongated, hair-like tube that emerges from the husk tip in a bundle. Each individual silk strand is directly connected to a single ovule, the potential future kernel.
The Mechanism of Wind Pollination
The pollination cycle begins with pollen shedding (anthesis), which typically starts shortly after the tassel has fully emerged. Tassels release pollen over five to eight days, with peak shed occurring around the third day. This release usually happens in the morning, between 8:00 and 11:00 a.m., as temperatures rise and humidity drops.
The sheer quantity of pollen produced compensates for the randomness of wind dispersal; a single tassel can generate between two and five million grains. Since corn does not produce nectar or scent, wind is its sole carrier. The wind catches the lightweight pollen grains and carries them across the field, with most settling within a 20 to 50-foot radius of the parent plant.
The silks, which are covered in fine hairs, efficiently capture the airborne pollen. Silks begin to emerge from the husks, starting from the base of the ear and progressing toward the tip over several days. For a successful harvest, the timing of pollen shed must align closely with silk emergence, a synchronization often referred to as “the nick.”
The Result: Kernel Development
Once a pollen grain lands on a receptive silk, fertilization is initiated almost immediately. The pollen grain quickly germinates, extending a pollen tube down the length of the silk strand. This tube delivers the male genetic material to the ovule at the base of the silk.
Fertilization of the ovule (the potential kernel) usually occurs within 24 hours of the pollen landing. The fertilized ovule then begins to develop, and the connected silk will rapidly dry out, turn brown, and detach, signaling a successful fertilization event. This direct link means every single kernel must have its own silk pollinated individually; a gap in the rows of kernels indicates an ovule that failed to receive pollen.
Factors Influencing Successful Pollination
The success of wind pollination depends on favorable environmental conditions, which can be disrupted by weather extremes. Severe drought stress is damaging because the silks, which are primarily composed of water, can slow their growth or fail to emerge from the husks entirely. This delay means the silks are not available to receive pollen during the brief window of anthesis, a failure to “nick” that results in poor kernel set.
High temperatures also pose a threat, as pollen viability is reduced when temperatures exceed 95°F combined with low humidity. Under these conditions, the pollen grains can dry out and lose their ability to germinate within a few hours. Planting corn in blocks rather than single rows is a common practice to ensure maximum pollen availability for transfer between neighboring plants, increasing the likelihood of ovule fertilization.