Detasseling corn is removing the pollen-producing flowers, the tassel, from the tops of corn (maize) plants and placing them on the ground. It is a form of pollination control, employed to cross-breed, or hybridize, two varieties of corn. Fields of corn that will be detasseled are planted with two varieties of corn. Removing the tassels from all the plants of one variety leaves the grain that is growing on those plants to be fertilized by the tassels of the other, resulting in a hybrid. In addition to being more physically uniform, hybrid corn produces dramatically higher yields than corn produced by open pollination. With modern seed corn, the varieties to hybridize are carefully selected so that the new variety will exhibit specific traits found in the parent plants. The detasseling process usually involves the use of both specialized machines and human labor. Machine detasseling Nearly all detasseling is done in two steps; the field is first detasseled by machine and then detasseled manually. Machine detasseling itself is typically a two step process. Initially a detasseling machine called a "cutter" goes through the rows of corn to be detasseled and cuts off the top portion of the plant. This is done to make the field more uniform so that a "puller" machine can come through the corn field a few days later and pull the tassel out of the plant by catching it between two rollers moving at a high speed. This removes the majority of the tassels. Detasseling machines typically remove 60 to 90 percent of the tassels in a seed corn field. This is far less than the 99.5 percent that need to be removed to produce the uniformity of seed desired by farmers. The main problems for the machines are that they are unable to adapt quickly to height differences in plants and they throw tassels into the air where they can become lodged in other corn plants and inadvertently allow pollination. It is desirable that the pulled tassel ends up on the ground to prevent this problem. Manual detasseling Whether or not a field of seed corn is initially detasseled by machines, eventually people are employed to detassel the plants that the machines missed and to remove any tassels that the machines left in the leaves of other corn plants. This is done either by having "detasselers" walk through the corn field removing the tassels or by