Onionology is complicated. Will try to clarify a little:

First a little background:

"onion" is a huge catch-all imprecise category encompassing a highly diverse clan, allium cepa and other allium species as well. What we are talking about here are bi-annual bulbing onions, grown from seed. All varieties of bulbing onions ultimately derive from the so-called "spanish" onion. They fall into two rough categories, long-day and short-day, based on how much daylight there is around the solstices where the plant is growing. So bulbing onions are highly sensitive to photo period.

The first most important thing to know is whether your latitude is "short" day or "long" day. As it happens, Kentucky is kind of in the middle, either might work though long day is probably more likely to do well. There are also a few hybrid varieties called "intermediate" day that might do best of all for you.

Short-day varieties are sown in fall and come to full size in late spring. They require more than just low latitude, they also require a mild winter climate, about z7b or warmer, so some regions of KY might work and others not. Long-day are sown soon after the winter solstice and planted out in early spring and are full size in mid to late summer, depending. An exception is the walla-walla which is adapted to the PNW and I think there may be one or two others long-days that can be fall-sown in mild northern climes.

So the infamous "sets" are small bulbs grown from seed and then planted to grow for the plant's second season. The plant really wants to bolt and grow seed rather than a bulb. Sets are a scam perpetrated by seed companies. They are mostly a waste of time and space. Buy plants grown from seed in texas next year, they come at just the right time for planting out and the results will be far better.

I'm in zone 6 as well. I grow long-day onions. For the last two seasons I bought Copra and Red Zeppelin (both good storing onions) from Dixondale Farms. These are plants. Plants with a long skinny stems.

I've seen onion plants bundled in the Spring, but the varieties sometimes aren't listed, and I want a variety that will store into the following year. Both these varieties have made it to January....until they were all eaten.

Plants seem to work out well for me. If you look them up they have a great growing guide and instructions on how to plant them. My plants went in the ground in early-mid April and were just harvested about 2 weeks ago. Pictures of mine can be found at the link below.

Hope this helps!
Kim

Here is a link that might be useful: My Garden...including onions.

That about covers it. I do disagree that it is complicated, but then we can complicate anything can't we.
Variety is important and that is true of anything we grow. The trick is to find a variety (cultivar) or varieties that best suit our growing conditions.
The easiest way is to start with plants of an appropriate variety. You can start your plants from seed, but it does add an extra dimension to your efforts. As for variety you will have to experiment a bit. Maybe start with Candy a popular intermediate day onion. I grew the long day sweet Spanish types in Southwest Virginia so I know they will grow in eastern Kentucky at least. Short day onions should not be grown where the ground freezes in winter.
Sets have a purpose, but they are long day storage onions. They will only bulb in the north. Most folks use them only to get a quick supply of green onions in the early spring.

I suggest that instead of looking in stores you order your onions from a reputable mailorder company. That way you can order a specific variety and know what you're getting.

Dixondale Farms!

This is a very helpful thread. Y'all have a gift for making difficult things very easy to understand. Thank You! I have my Granex 33 seeds and will be sowing them in about a month. I could not find any mail order plants, since the places I checked were sold out. No matter. I am pretty good with seeds, so I expect to do fine with them.

Can anyone tell me of Dixondale grows onions for other suppliers like Johnny's and Territorial?

Two years ago, my friends and I went in on an order from Dixondale. The starts did not do well at all. Big disappointment. This past year, we ordered from Territorial and Johnny's and honestly, the packaging, labeling, etc. looked identical. The only thing that was (very) different was the price.

Inquiring minds want to know... :-)

Most seed vendors drop ship. That is they relay plant orders to a plant company with which they have a contract. Dixondale, Browns Omaha, Onion Shed, etc are in the mix

I have used Brown's a lot (why not, same surname they must be good folks?), and always been pleased with what they sent, even if I havn't always made good use of the plants.

farmerdill, that is what I suspected. It is ridiculous to think that Johnny's raises their own starts!

pn, I will take a look at Brown's.

The prices at Dixondale were so low as to be almost unimaginable. I ordered for several of us and really got burned....nothing produced well at all. But, it was 2009, the year of endless rain and the subsequent late blight....just a tough year all around.

This year, I let one of the others order and she spent about three times what we did the year before. Varieties were the same, only some were organic, and the presentation was identical. Dixondale's discussion of chemical use makes me a little squeamish, I will say...