I have not grown Evergreen, but it is a very popular scallion and quick to make green onions. http://www.denverplants.com/veg/html/alliu_cep.htm While this site offers the standard " sow one month before last frost date" this type of onion is popular as as an overwintering onion in England. So I would expect a fall planting would work for you. It is a single stalk onion, not a multiplier. They take approximately 75 days from emergence to table. Of course winter growing is much slower.
Bunch actually means bulbless onions that that you pull and tie up in bunches for market. Alternate names are scallions or salad onions. Onions that divide into multiple stalks are multipliers/shallots/potato onions.
There are some bunching onions that bunch. Or are supposed to bunch. This Fall I have planted all kinds of Onions, garlic and Leeks.
The Type of bunching onion I bought that I think will bunch is named "Hi Shi Ko". With true bunching onions, you leave a few so they can "bunch back up".
so now, in Central Georgia, in Oct 2010, The seeds are up and in the ground here. I also planted some in a long container. They look like they want to bunch! haha. Will keep you posted.
I live 8000ft in Colorado. My friend has bunching onions growing in his gound beds that survive winter lows of -20F. He has lots of mulching over them. He also is snug against a rather large and treed hillside. I did not think this was possible. I am making a raised bed, will they survive there also? I am in a more open housing development without trees and brush windbreaks.
You should care for them the same way your friend does and hope for the best. Even a bed on the south side of a house or shed is better off than no help at all. I suspect your friend actually has 'multiplying' onions, though- see above from Farmerdill explaining a true bunching onion.