Sweet Corn

I normally wouldn't do this but this post is a direct cut and paste from a Harris Seed Company email sent to customers and potential customers.  I love sweet corn and couldn't write this better.  Here is plagerism except I am giving credit.  Even got the author's picture. 


Sweet Corn Genetics

Customers often ask about the different genetic types of sweet corn we offer. Here I will try to give you a quick lesson in sweet corn genetics. There are five basic genetic types of sweet corn we offer: normal sugary (su), sugary enhanced (se), synergistic se (sy), supersweet (sh) and augmented supersweet (shA).

Normal Sugary (su) is the standard sweet corn and is the one you've known from many years ago. These varieties have good corn flavor, and their quality is best if picked and eaten the same day. When picked at full maturity the quality is good, but it soon depreciates after full maturity has been reached. Most normal sugary varieties germinate quite well at soil temperatures over 55° F and grow with good vigor. The only (su) variety we still offer is Silver Queen.
Isolation note: Normal sugary varieties should be isolated from supersweet varieties (sh and shA), field corn, popcorn and ornamental corn. They may be planted beside sugary enhanced (se and sy) varieties.

Sugary Enhanced (se) varieties have elevated sugar levels, better tenderness, and higher kernel moisture levels as compared to (su) varieties. The result is a sweeter, tenderer kernel with good corn flavor that will retain its eating quality longer than a normal sugary variety. Most (se) types prefer slightly warmer soils (above 60° F) for germination. Synergistic se (sy) types are very similar to the (se) types, but the breeders have incorporated some supersweet kernels into the ears to give the varieties an extra punch of sweetness. As a whole, these types tend to have a tenderer kernel and will hold slightly longer at full maturity than the standard (se) types.
Isolation note: (Se) and (sy) varieties should be isolated from supersweet varieties (sh and shA), field corn, popcorn and ornamental corn. They may be planted beside each other and normal sugary (su) varieties.

Supersweet (sh) varieties have a shrunken gene, so named to describe the lightweight, wrinkled seed of this type. This gene raises the original levels of complex sugars and extends their flavor by slowing the conversion to simple sugars and finally to starch. Supersweets' kernel moisture is retained longer, and their ears have a much longer holding period after they reach full maturity, both on the plant and after harvest. The earlier introductions of this type had a kernel texture that was noticeably crunchier and firmer than other genetic types. However, with the introduction of Augmented Supersweet (shA) varieties, breeders have improved the tenderness considerably from what it used to be. Supersweets do not normally germinate well under less-than-ideal conditions. Wait for ideal growing conditions (soil temperatures of at least 65° F and moderate soil moisture) before planting supersweet varieties.
Isolation note: Supersweet varieties (sh and shA) may be planted beside each other but need to be isolated from all other genetic types of corn, including (su), (se) and (sy) sweet corn, field corn, popcorn and ornamental corn.

* Because corn is wind pollinated, isolation as discussed above can be achieved by separating varieties by: 250 feet of distance, an effective wind break, or 12-14 days difference in maturity time