With monsoon season upon us, Baja Arizona is coming into its second corn-planting season. Whether corn is planted in a three sisters garden with beans and squash or methodically planted in its own blocks, we go for the fast maturing varieties this time of year to take advantage of the rains and the last bit of warmth before our nights begin to cool down in the fall.
Corn (Zea mays, also called maize) has been a prominent part of human culture for a very long time, but if it weren’t for us meddling humans, the crop wouldn’t be around at all. Corn as we know it doesn’t exist anywhere in the wild, and it certainly didn’t first appear as the sweet treat on the cob that we enjoy today. The development of sweetness came fairly recently in our long, intertwining history with this highly variable crop.
The most widely accepted theory of corn’s origin is that some astute agriculturalists in southern Mexico first adapted it from a grass called teosinte around 9,000 years ago. Though the vegetative parts of maize and teosinte look somewhat similar, the flowering and fruiting structures appear so unrelated, and corn showed up so suddenly in our agricultural history, that it was difficult to convince the scientific community that corn, the world’s third most important food crop, was likely derived from a wild grass that grows in southern Mexico.
After genetic testing and years of crossing different corn varieties with teosinte and with each other, producing an astonishing array of results, scientists were able to figure out that just a handful of Zea’s genes can make a big difference in the physical properties that it displays. Changes in these genes have drastic results in a short amount of time, which likely explains why corn appeared so suddenly in human culture. The evolutionary process is typically seen as a slow and gradual process but, in the case of Zea mays, significant changes can be made quickly by modifying one of a small number of genes.
Maize has plenty of other genes that influence its properties in less striking ways, but this doesn’t mean that they’re insignificant. Slight changes can make all the difference when you’re looking for specific results. When early agriculturists first began selecting corn, certain kernels were chosen, preserved, and planted for qualities that made them more valuable in one way or another. Some might have been easier to grind into flour, stayed attached to the cob better than others, or just tasted better. Those that resisted pests and stored well were more likely to make it to sowing time the next season.
The first corn varieties didn’t include the sweet varieties that we know today. Indeed, corn was often ground or popped; it was rare that anyone would have eaten it fresh off of the cob. Sweet corn happened spontaneously in a field, much like the first sweet Red Delicious apple (read Michael Pollan’s The Botany of Desire if you haven’t heard about the origin of sweet apples). Though we typically think of sweet corn as being golden, it turns out that the flavor of corn has very little to do with its color.
The first sweet corn varieties had mostly white kernels, and they weren’t available to purchase in seed catalogs until the 1820s. Golden sweet corn didn’t become the preferred color until the early 1900s, when the first all-golden sweet corn, Golden Bantam, was developed. There are many other colors of delicious sweet corn to explore. None of the sweet corn varieties available in the 2017 Native Seeds/SEARCH catalog are all-golden—start here if you want to grow a sweet corn that will do well in our climate.
According to the National Corn Growers Association, the largest percentage of corn we produce commercially in the United States is grown to feed livestock; the second largest percentage goes to ethanol production. The corn grown for these purposes is a type often referred to as field corn. Only nine percent of our commercially grown corn includes the sweet corn varieties that are typically eaten fresh. Different types of corn also included in this small percentage are used to make food products such as cornmeal or corn flour, and industrial products like adhesives and varnishes.
Thousands of corn varieties are grown around the world to match local needs and individual growing conditions from mountain tops to desert valleys. This crop is so adaptable that just about everyone can grow it. The Corn Belt in the Midwestern United States is the most productive region in the world, owing partly to the area’s favorable soils and climate, and partly to the types of hybrid varieties that are grown there. Less productive varieties are grown in parts of the world where conditions aren’t as favorable if it means that there will be something to harvest.
There are six major groups (or races) of corn typically recognized today, but others exist that are grown for specific purposes. Most of what we grow in the United States are hybrid varieties of dent corn, though hybrid, heirloom, and open pollinated corn of all types are popular with homesteaders. It all depends on what you want to use it for.
The most common commercially grown corn in the United States is dent corn, mainly because it is highly productive here. The indicative dent in the crown of each kernel occurs because the kernels have an especially soft, floury interior with hardened sides. These varieties are used primarily for livestock feed, but they can also be used for dry or wet milling to produce tamales, tortillas, syrups, fuels, and corn beer, to name just a few products. In the Southwest dent corn is also roasted to make elote.
Flint corn generally has a smooth, hard outer shell and a grainier, less starchy interior, though some varieties are more starchy or floury than others. It can be used in many of the same ways as dent corn, but it isn’t as productive, so it never gained popularity in our commercial market. The hard-as-flint outer shell makes these varieties easier to store and more resistant to pest damage.
Popcorn is possibly the oldest type of maize that we grow to this day. It’s hard outer shell can place it in the category of a flint corn, but it features a smaller kernel with just a modest amount of starchy interior. There are two main types of popcorn; pearl, which has a round shape, and rice, which is more elongated. As the name suggests, we mostly grow this race of corn for humans to eat as popped corn, but it’s also used to make pinole.
Another one of the oldest races of corn still grown today is flour corn. These varieties are characterized by a softer shell and a uniformly soft and starchy interior, which makes them particularly easy to grind after they’re dried. As the name suggests, they’re primarily used to make corn flour, though they can also be used to make cornmeal (when ground less finely), hominy, and elote. Arid climates are the best places to grow flour corns since they’re susceptible to molds in higher humidity. They may be better choices for springtime planting in Baja Arizona for this reason.
The type of corn that most frequently makes it to your plate in fresh or kernel form is sweet corn. This race is subdivided into three main types: sugary, sugar enhanced, and supersweet (sometimes called shrunken). The genetics in these varieties allow for extra placement of sugars or different types of sugars, or they slow down or prevent the conversion of sugars into starches. Sweet corn is primarily grown for direct human consumption.
We grow pod corn mostly for ornamental purposes. Look up a photo and you’ll understand why. Each kernel is encased in a leaf-like structure called a glume, which makes them extremely interesting to look at but a lot more difficult to process. Although it has long been thought to be a primitive, wild ancestor of today’s edible corn, genetic studies have identified it as a more recent mutation in the genes of corn that was already domesticated.
Our region was one of the first in the Americas to grow domesticated corn, so there are quite a few varieties that are well adapted to growing here. Many people prefer growing corn this time of year because heat and dry winds that occur earlier in the year can be detrimental to pollination, resulting in spotty kerneling.
Many types of corn must be kept from cross-pollinating if you want to get the expected results at harvesting time. Since our growing season is short this time of year, it may be more difficult to stagger planting/flowering times. Instead choose varieties that won’t cross-pollinate, plant only one type, or separate each type by a buffer zone of at least 150 feet or taller plants that will help block pollen movement.
Insects and diseases are more prolific during and after monsoons. A dab of mineral oil on the silks when they’re still green can help keep corn earworm at bay, and well-timed applications of organic pesticides like spinosad can help control stalk borers. Local, heirloom varieties are often more resistant to the pests that are known to occur here, so shop local when you can. ✜
Amy Belk is a garden writer and photographer, a certified arborist, and a certified nursery professional who has been learning from her garden for 16 years. She and her husband homestead on a little piece of the desert in the heart of Tucson.