What is the visual difference from sweet corn and field corn?

Answer 1

A great video that covers the differences and has great descriptive pictures can be found in the related links. Otherwise the description below is fairly accurate...

Sweet corn may have up to two ears growing from one stalk, while field corn may have one, two, or even three ears per stalk.

Field corn grows very tall, very quickly and has big, broad leaves. Sweet corn grows much shorter and has thinner leaves that are more spread out on the stalks. The flower on sweet corn appears earlier in the season than "cow" corn.

Field corn isn't palatable to most of us used to sweet corn, it is mealy and has little sweetness. In many countries though, in for instance Central and South America, it is eaten like sweet corn and used in many dishes and preparations. It's primary use in the U.S. is for livestock feed, corn meal, and increasingly, ethanol.

Sweet corn has evolved greatly over the last 30 years. plant breeders have developed excellent new varieties of yellow, white, and bi-colored corn (often called butter and sugar which was actually the varietal name of one of the first bi-colored corns). The new SE or sugary enhanced corns retain their flavor longer than the old standard ones. Most local growers, at least in the northeast U.S. grow these varieties. Super sweet varieties hold even longer, enabling them to be shipped longer distances and sold in supermarkets, but they have a crunchy texture and less corn flavor. Purists will tell you that sweet corn should be eaten the day it is picked, but the new SEs allow it to hold for 2 or 3 days, especially if refrigerated. Sweet corn should be refrigerated as soon as possible after being picked to get out the "field heat" and kept that way to lessen the heat of respiration that all fruits and vegetables produce after harvest

The main difference between sweet corn and field corn is how early it is harvested. All corn kernels start out as "sweet", meaning the carbohydrates are mostly in the form of sugars. At this point, there is a lot of water in the kernels, so they are also tender and easy for humans to eat. As the plants mature and and the kernels dry, the sugar is converted to starches, and the kernel becomes too hard for humans to eat. At this point, it's called "field corn".

Now, there are some varieties of corn that have more sugar in the young kernels, and are thus "sweeter" than other varieties or corn, and therefore more likely to be planted for sweet corn. But if you leave the so-called "sweet corn" varieties in the field long enough, you're still going to get field corn. Likewise, there are corn varieties with attributes better suited for field corn. But if you harvest them early, they can be eaten by humans. They're not nearly as sweet as what you might get from a can, but they're edible. I grew up on that, in the southern US.