Much depends on how much work you want to do to harvest earlier onions. I started some bulbing onions about a month ago on the same day as I started leeks. The reason for starting these early is that I want pencil thick stems to transplant through black plastic mulch. Thinner stems tend to end up under the plastic and dying. But in addition to cutting them back I feel that I need to do one transplant after seeding into a deeper flat and seperate plants within and between rows by 3/4" to avoid crowding. This step doubles the work of starting onions. For bunching onions I feel you can start them almost anytime now. Mine are up and I plan to just trim and water those flats for the next month and then pull the matted roots apart when planting them in a furrow. There is alot of plant size variation with this method but I harvest by thinning the largest ones first and that allows harvesting over a 5-6 week period.

Onions are no different than any other seeds when it comes to containers. ;) The Container FAQ here offers many suggestions and a picture of many and they will all work for onions too. Link below is to a previous discussion with even more suggestions unless you want to invest in more professional seed starting set-ups. Search 'container' for even more discussions and ideas. As to number of seeds - onions are usually sowed quite thickly and then thinned as needed or transplanted so you can just scatter sow the seeds all over the top of you soil in whatever size container you choose to use. Dave Here is a link that might be useful: Favorite seed starting continers to use discussion

You should have good luck with the granex types in Atlanta which are what Vidalias are from just a bit south. Check your Georgia extension service for cultural information; they have been intimately involved with commercial development of that variety of onion. As I understand it, the process starts with thick early fall planting of seed for transplanting later in the autumn to a better spacing in production beds to winter over to a late spring or early summer harvest, but you should be able to get specifics from the extension service. Else you can almost certainly get bunches of started plants for spring planting from quite a number of sources. That's what I do up here in Minneapolis with good results for Copra and cipollinis, or you can grow your own sets from a late thickly planted bed of seed that matures mid to late summer for planting back the next spring. My parents did that for years back when I was growing up. My mother always got a good crop of onions off her sets.

Thank you Farmerdill! Very much appreciated.