I planted both kinds the 1st wk. of March...I pulled a few today and the bottoms are small, but the tops are well over a foot long. How much longer for the bottoms to get larger? I'm in zone 8 btw.
Here in our area, onions start to bulb around June/July. Might be a little bit earlier in your area. We were talking about onions a week or two ago so you might want to look for that thread. If I remember right, it was titled " Onion question" and it shouldn't be much past page 2 or 3 in the fruits&vegetables section. Or we can always start talking about it in this thread
I am in Zone 4 (pretty much the north pole!) I planted onions at the beginning of April and I won't expect to harvest them until fall... I had great success last year, and didn't have to purchase onions until January. Nothing thrills me, like growing my own food!
I read somewhere that the summer solstice is what makes the bulbs start to really develop, so probably around the end of June they'll start getting really big.