Corn, Zea mays, which most of the world outside of the United States knows as maize, is one of the most useful cereal crops of the world. Today in the United States and much of the developed world, corn is mostly fed to animals. But historically in the United States corn was a major source of direct sustenance for humans as it still is today in much of the developing world .
To understand the open pollinated corn story we need a little corn botany and genetics lesson. Sorry, you may stop reading now and wait for the next post if this makes your hair ache. Corn is a monoecious plant. That is, it has separate male and female flowers on the same plant. The tassel is the pollen producing male flower and the ear with silk is the female flower. (See diagram link) Corn is wind pollinated and normally it is cross pollinated, that is, pollen from another plant pollinates the female flower on a given plant. This process of natural pollination by the wind resulting in cross pollination of individual plants is sometimes referred to as “open pollination”.
Until about 1930, all of the corn grown in the United States and elsewhere was from seed which had been produced by this process of open pollination. Individual open pollinated varieties of corn had a great deal of genetic variability. That is, although individual plants within a variety looked a lot alike and had similar growth characteristics, each plant actually was unique and had a slightly different mix of genes from every other plant. In the early twentieth century corn breeders discovered that if they developed two inbred lines of corn and then crossed (hybridized) them, the resulting seeds would produce plants that were more robust than either of the two parent plants, a phenomenon known as hybrid vigor. If the breeders produced many plants of the two inbred lines and crossed them, the resulting seed could be used to plant acres and acres of corn that was not only robust, but each plant was genetically exactly like every other plant. That meant the plants would all grow at the same rate, mature at the same time, and grow to be the same height, assuming similar environments. This was ideal for machine harvesting of corn. Furthermore, these hybrid varieties, as they were known, had surprisingly higher yields than the old open pollinated varieties from which they were derived. The harvest advantages and yield advantages combined made hybrid corn varieties very attractive for farmers, despite the fact that the seed was expensive and new seed had to be purchased each year (More on this in the next post). By 1950 nearly all of the field corn and sweet corn produced in the United States was hybrid corn, truly an agricultural revolution.
The production of hybrid seed was fairly simple in theory, but quite labor intensive in practice. Rows of male parent plants had to be planted next to rows of female parent plants. The tassel needed to be removed from the female plants to make sure that only the pollen from the selected male parent pollinated the female parents. Resulting seed was then harvested from only the female parents. To avoid damage to the female plants, the tassels had to be removed by hand. And the kicker was that this whole process had to be repeated every year as grain from a hybrid variety could not be saved and replanted the following year. Very quickly many high school students in the Midwest had a guaranteed summer job. All you had to be willing to do was walk up and down miles of corn rows in the hot sun removing tassels. – Herbivore Reed
Next: Why Hybrid Corn Seed Can’t Be Saved and Unintended Consequences
Corn Diagram Link:
To read more about the history of hybrid corn: