I always seem to have problems with onions every year. Leeks and scallions are much easier to grow in my own personal opinion. For one thing, my onions never seem to germinate consistently though I seem to have gotten a good batch of seeds this time around. I'm growing a yellow and red variety - 'Copra' and 'Ruby Ring'. Also, I haven't been able to grow an onion larger than two inches in diameter. But I plan on doing things a little differently this year, which I hope will pay off come harvest time. For starters, during the past two years, I've tried growing onions both from seeds and from sets. Both years, most of the onion sets I planted ended up bolting so I'm done with them. Also, I'm not setting my onions out this year until the weather has warmed up significantly (maybe the last week in May here in Vermont). Hopefully that helps too. If anyone has any additional onion growing advise, please let me know!
Finally, I had wanted to start my onion seeds in soil blocks but haven't been able to source the ingredients. I ended up sowing 3 seeds in each plastic cell. Now I have to decide whether to thin them now or let them be. When grown together, onion seedlings are generally easy to divide at planting time so I may just let them be. Though I'm sure they'd be much happier thinned down to one at the start. What do you think?