Tasseling is just around the corner for most corn fields. The acres of green will soon be topped with shades of yellow, green or purple. What an exciting time in the life of a corn plant. The emergence of tassels not only marks the halfway point of the corn’s plant life but also signifies a major change within the corn plant.
A major shift of priorities occurs once a corn plant tassels. Prior to tasseling, the corn plant is in a vegetative growth stage. The corn plant is focused on producing vegetation such as stalks, leaves and roots and maintaining a healthy defense system. Soon after tasseling the corn plant no longer is concerned about growth or maintaining a strong defense system, but the sole purpose of the corn plant becomes producing grain. All of the plants resources are redirected from plant growth to the formation of the largest ear possible.
Driving down the road, the tassel is easy to recognize, but what is involved with the tassel? The tassel is a male flower. Remember that the corn plant contains both male flowers and female flowers (corn silks) on the same plant. The tassel consists of many smaller parts that work together to release pollen. The tassel itself consists of a center spike with varying amounts of branches. The center spike and branches hold structures called spikelet flowers. The spikelet flowers then hold the anthers (look like double barreled shotguns) and finally the anthers hold and release the pollen.
The tassel has many built in safety control features to ensure the corn plant carries out a successful pollination. The first safety measure surrounds the emergence of the tassel from the corn plant. Pollen will not begin shedding until the tassel is fully emerged. The second safety measure ensures pollen is present when silks are most receptive. Tassels typically begin releasing pollen two or three days prior to silk emergence. By having pollen present when silks emerge, there is ample opportunity for silks to be pollinated. The third safety measure focuses on the fact that not all the silks emerge at once. Therefore, the entire tassel does not release pollen at once, but instead pollen shed usually begins at the center of the spike and then continues upward, downward, and outward over time with the lower branches being the last to release pollen. Pollen is shed for a total of five to eight days depending on the hybrid. The heaviest pollen shed period occurs on the third day. The extended pollen release almost eliminates the possibility of a total pollination failure.
Pollen shed is critical to pollination success. To ensure pollination success, the tassel has built in a redundancy factor into the tassel. Pollen grains are developed in and dispersed by the anthers. The anthers are the structures that hang from the tassel during pollination. Each tassel contains two to five million grains of pollen; this equates to 2,000 to 5,000 grains of pollen for each silk. More than enough pollen will be present since only one grain of pollen is needed to fertilize a single silk.
During pollination, pollen shed is not a continuous process. Pollen is released from the anthers only when temperature and moisture conditions are favorable. The anthers open and allow the pollen to pour out after dew has dried off the tassel. All the pollen from a single anther may be released in as little as three minutes. Spent anthers eventually drop from the tassel and are sometimes mistaken for the pollen itself when observed on the leaves or ground. The peak pollen shed period is in the morning between 9 a.m. and 11 a.m. A second pollination period can occur in late afternoon or evening as temperatures begin to cool.
The tassel is a critical part of the corn plant’s ability to produce grain. There are many amazing details about how the corn plant works, the redundancy of over producing pollen, the tassel’s ability to shed pollen only under favorable conditions or when the silks are present, to name just a few. The corn plant is an amazing creation that when understood and managed can produce large rewards.