You won't regret the Polka(70d) selection. If you like the synergistic selections as I am leaning toward you may want to give in to them for the entire season. Followup excellent bicolor choices are Charisma(74d)and Providence(82d). I'll admit that the choice is highly subjective. I was raised on IoChief and Silver Queen, two huge eared varieties that my parents loved and I thought were better suited for livestock feed. But although my prefered corn for eating is a SH2 variety, I find that the isolation requirements and poor germination in colder soils make them harder growing choices. The synergistic varieties get my vote as both grower and consumer. It isn't surprising that people are paying more attention to Kernel texture in their preferences. But while some would consider a variety like Incredible to be very tender, others might call it mushy. So to help you to decide for next year I'd suggest that you visit a few farmers' markets in your area and purchase a few dozen ears from vendors who will reveal the names of the varieties that they offer. If you are drawn to one variety you can return and ask the grower more about that variety.

There is always the element of risk in any crop and early sweet corn can be frustrating, especially when yo get a reasonable crop only to dislike the eating quality. For my part I am content with a slightly later crop but others have had limited success with transplanting or using modified planting techniques to protect from early planting losses. Timing is critical when transplanting. I've heard that a 3 day delay in a 21day seedling can be disastrous. Even planting and covering with plastic is no gaurantee that a late hard freeze won't wipeout your crop. I have developed a liking for the synergistic varieties and was recently saddened to see that "Polka" an early bicolored syn. variety was replaced with "Pay Dirt". I'm giving the replacement a try this year in hopes that it will be as good as "Polka" was. Its a 65 day bicolor but if it is like other early varieties the raccoons need to get on their knees to eat the ears off the stalks. Don't expect tall plants or big ears from early varieties.

Only certain varieties of sweet corn will have their flavor affected by a nearby field corn planting. These are the ones labeled "super-sweet," "sugar-enhanced," etc. That's why some of the advice above is incorrect -- though it would be true for "ordinary" vegetables (and non-enhanced varieties of sweet corn, for that matter). You could try timing your planting to avoid cross-pollination, but I wouldn't rely on starting indoors; direct-sown corn catches up quickly to transplanted. Or simply plant a variety of sweet corn that doesn't become starchy if cross-pollinated. Some people prefer these; their disadvantage is that the corn must be eaten very quickly after harvest, while the enhanced varieties can keep their sugar for days. Here is a link that might be useful: Sweet corn

I have the same variety - Northern Xtra Sweet. My corn has fallen in years past...Easy to fix - in one shot! In addition to mounding some dirt, I now keep mine permanantly supported. Put a 4 or 5 ft tall stake at each end of the row, tie a strand of wire to each stake - going down each side of the row(a loop) about halfway up the overall hieghth of the stalk - make sense? You might slide the wires up as your corn grows. Also, I "pinch" the strands at a few intervals along the span w/ a twisty - this helps keep it taunt. Its simple and you only have to do this once... Besides tilling in all purpose ferts before I plant, I also use urea when the corn is 1 ft tall and once more when the tassles start to appear. One 16 oz cup of urea per 100 ft row - so about 8oz for your 4 rows (48 ft). Your corn is not tasseling early...Once you can start to see the tassles inside the plant, the stalks will grow another 2-3 ft (or more) before the tassles actually "come out". You're fine! With only 4 rows, you might need to hand pollinate your corn to help INSURE good pollination. It really is easy, but timing is everything here...Search this forum for "hand pollinating corn", but basically all you are doing here is rubbing the tassles on the silk... at the right time...