I think onions won't bloom and go to seed until the second year. So I'm not sure it cares much when you plant it.

When does its' second year start?

Onions are biannuals. Year one, it grows from seed to a bulb. Then it has a dormant time. Year two is when that bulb wakes up and has a full season growth cycle, allowing the scape to bloom.

A year one onion can be left in the ground to overwinter, then come back for it's seed growing year two. Or a mature year one bulb can be planted in the spring and grown out to bloom. For best results of good seed.

It can happen that a gardener misses a bulb and it pops up in the spring. Those often can produce a good seed head. Sometimes bare root starts are handled in a manner that triggers the onions dormant and wake up cycle. But often that's unreliable, since many people don't get blooms off those in the first year. Same goes for those little bulb onion starts you see in the spring. Those are technically ready to start their second year, but often just grow big and don't reliably produce good seeding blooms.

I'd planted seeds in April, got bulbs in July, they just stopped to grow and their tops dried. I think it is sweet kind of onion, not sure long day or short day, but I don't know will it survive till spring . So I want to plant it now and let it grow. Since it has some dormancy period already, is it possible that it will bloom till December -January?

In previous years, bulbs left in ground were blooming in winter. I just didn't pick those seeds and didnt know their ability to germinate .

Plant in April, bulbs in July? Maybe you mean itsy bitsy tiny premature bulbs? I plant in November and harvest full-sized onions in May. Bulb formation doesn't even really start to happen until late March. Not sure where you are, but maybe the tops dried prematurely because of intense summer heat? I would have thought you needed mature bulb formation before dormancy could happen. But if you saw blooms after premature bulbs, you might be good to go.

Yes, I could say it is premature. It should be up to 1.5 lb bulb according to the seed package discription. I 've got 9 bulbs 2" dia from that package. I know I plant it in wrong time for growing full size, but I planted as soon as I could. If I would wait till November or later I wouldn't get germination at all.

If you planted in April, I can imagine that you have small bulbs now in September. They should be mature in October (look for the leaves starting to brown and fall over). That's when you hack off the leaves at ground level, and wait until the bulbs resprout in the spring. Those plants will produce flowers and seeds later in the year.

Onions can be a great addition to your garden! In zone 7b, you can start your onion seeds indoors in late winter or early spring, and then transplant them outdoors once the risk of frost has passed. If you plant onions now, they will likely begin to grow, but the blooming process generally occurs in the following spring and summer, not during winter.

Onions are biennial plants, meaning they typically produce flowers in their second year of growth if left to mature. If you do grow them to flower in their first season, they may not set viable seeds in winter since most flowering and pollination occur in warmer temperatures.

When it comes to pollination, onions are mainly insect-pollinated, but wind can also assist in the process. If you have flowering onions in your garden during their blooming period in spring, pollinators like bees will likely visit them. However, if you’re worried about the timing of flowering and pollination, ensure that you allow your onions to go through their full growth cycle before harvesting, which will increase your chances of getting good seeds.

So, if you plant now, just remember that it's best to plan for next spring when they will be in their prime for flowering and pollination. Happy gardening!