I haven't tried onions, but I did try leeks! ...which is sortof an onion :) I grew them from seed, and they actually did better than I expected, but I didn't take care of them like I should have. Didn't give them enough water. Something also got to them from underground -- some of them had these little "trails" where bugs has been munching on the surface.

I grew them in a milk jug and separated them when they were big enough. They didn't seem to mind that at all!

It was worth the experiment. I think I got them from John Scheepers Kitchen Seeds.

I don't know if this helps you, but it was a fun little experiment!

Leisa

I take the root tips of the green onions used in cooking and just toss them at the back of a border and cover them. Each year I get a few attractive inflorescence. I do it for the flowers, not to produce anything consumable.