I do not know your climate (temps, length of growing season), therefore , I cannot make any specific recommendations. But let me give you an example; I am in zone 7b(PNW) but our HEAT ZONE is 1. Our first statistical frost date is in mid November and we have generally mild winters. Now here is what I am going to do tomorrow:
I have already purchased bunching onion seeds . I will start them in batches and later on (after establishing)I will separate them and transplant in the garden for fall/winter. Onions are very transplant friendly and forgiving for mishandling during transplanting. So , if you get them in clumps, it is quite easy to eparate them, by soaking in water and shaking a bit. Never throw away a single seedling.

I have not seen any nursery to sell onion seedlings for fall planting yet.

Whenever you are in a supermarket, see if they have some small green onions in bunches with bits of roots. Trim them back to about 5 inches and plant them. They will regrow in a couple of weeks.

With scallions, you also can cut off the bottom 3/4 inch with roots attached and replant it. It will regrow at least once.

With scallions, you also can cut off the bottom 3/4 inch with roots attached and replant it. It will regrow at least once.
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well, yes planatus, you can do that. Then why bother growing them if you want to buy from the grocery store ? plus, the bottom part is has more flavor than the top.

I

You could buy some pearl onions at the grocery store and plant those to use as green onions. Although I'm unsure of the cost of pearl onions so I don't know if it's worth it or not.

Rodney

Pearl onions are used as onion sets. Depending on the size there could be 70 to 100 of them in a one pound bag, selling for $4.00 ???. Not bad for getting fast results. Several years ago I fall-planted them and some in the spring. A lot of them bolted, so I just used then as scallions.

I tried to grow onions from sets and none of them grew a bulb. I cut the green stalks and used then as green onions.

Perhaps the garden center has some left over sets from spring.

The poster was working with containers. When you're doing square-inch gardening, the point is to keep it going and have fun.

In winter I like keeping a pot of scallions in the sunniest window. I weaken them terribly with constant snipping, but wouldn't be without them.