there are two keys That I am aware of. 1. Variety, many are developed to resist bolting while others mostly older varieties bolt at the drop of a hat. 2. Timing. These onions are planted in the fall. Too early and they get a lot growth followed by a cold snap that cause dormancy. It is the breaking of dormancy that leads to early bolting. Hopefully you live on the zone 8 coastal plain which is suited to short day onions,

I am a procrastinator usually, so I am not getting them in too early. But, I think I will do more research on which varieties resist bolting. I usually go with Walla Walla and a couple others. That could be a good start. Thank you

Walla Walla is a Sweet Spanish type not really suited to over wintering. Look at short day varieties. like Hi-Keeper. Here is a link to an earlier discussion. http://forums.gardenweb.com/discussions/1718819/overwintering-onion-in-the-pnw