Corn pollination is the biological process that determines whether an ear of corn will develop kernels, directly influencing the final yield. This event involves the transfer of pollen from the male to the female parts of the plant, which must happen successfully for fertilization to occur. Learning to visually assess this success is a valuable skill that allows for an early evaluation of the crop’s health and potential. By observing changes in the plant’s reproductive structures, it is possible to confirm that the necessary steps for kernel formation have been completed.
The Roles of Tassels and Silks
The corn plant features separate male and female reproductive structures on the same stalk. The male flower, known as the tassel, emerges from the top of the plant and is the source of the pollen grains. Each tassel contains thousands of anthers, which release millions of pollen grains, typically during the mid-morning hours after the dew has dried.
The female flowers are located on the developing ear shoot lower down the stalk, and their stigmas are the long, thread-like structures called silks. Each silk is directly connected to a single ovule, which is the potential kernel on the cob. Silks are covered in fine, sticky hairs designed to catch the wind-borne pollen grains.
A pollen grain must land on a receptive silk, germinate, and grow a pollen tube down the length of the silk to reach the ovule. This process typically takes between 12 and 28 hours. Silks from the base of the ear emerge first, and those at the ear’s tip emerge last, meaning pollination occurs sequentially along the ear.
External Signs of Pollination Success
The most reliable external sign of successful pollination is the transformation of the silks. Fresh, newly emerged silks are light green or yellowish, moist, and sticky, indicating they are ready to receive pollen. These silks will continue to elongate for about a week if they do not receive pollen.
Once a silk is successfully pollinated and the ovule is fertilized, it detaches from the developing kernel, dries up, and rapidly changes color. Within one to four days after fertilization, the silk will turn brown, curl up, and begin to shrivel. This mass of dry, dark, shriveled silks emerging from the husk visually indicates that fertilization has been completed.
If a silk remains long, fresh, and green, it signals that it has not received pollen or that fertilization was unsuccessful. Silks that were not pollinated do not detach from the ovule, meaning the potential kernel will not develop. The browning of the silks is a direct, observable result of the successful fertilization of the ovule.
Physical Confirmation of Kernel Set
While silk browning is a good indicator, a physical inspection provides definitive proof of kernel set. This check involves carefully peeling back the husk leaves from a developing ear, taking care not to completely remove them, then gently shaking the ear. Silks from fertilized ovules will easily fall away, while unfertilized ovules will still have their silks firmly attached.
The proportion of silks that drop off indicates the percentage of ovules that have been fertilized. A lack of kernels, particularly at the tip of the ear (known as “tip back”), often correlates with silks that remain attached, indicating pollination failure in that area. This inspection can be performed 10 to 14 days after silking, when the ovules are in the “blister” stage and appear as watery, whitish swellings on the cob.
A later, more detailed confirmation of kernel development is the “milk test,” performed when kernels reach the R3 (milk) or R4 (dough) stages, approximately 18 to 28 days after silking. To perform this, a kernel is pierced or squeezed to check the consistency of the fluid inside. Kernels in the milk stage exude a thin, milky-white fluid, while those in the dough stage contain a thicker, more pasty substance as starch accumulates.
The presence of this fluid confirms that kernels are actively developing after successful fertilization. This stage is a reliable sign that pollination was successful and that the plant is progressing toward maturity. By the dough stage, kernel abortion is much less likely than in the earlier blister stage.