Flowering is generally rare in this type of onion. Rare enough that some of us will never see a flower head in our multipliers. Seed that may result often germinates poorly and may produce all kinds of different onions, some of them may be worthwhile to keep and propagate, if you want to go to the trouble.

For best keeping when this happens pick off the developing bloom as soon as you can identify it. IMO if you prune off the developing flower heads keeping is only minimally affected which is somewhat different from normal onions, where keeping is much more adversely affected. Leave as much of the stem as possible.

FWIW potato onions seldom bloom and for the most part there is no forecasting when they do so either, although it is my impression that fall plantings are more likely to try to bloom than spring plantings.

I did plant them in the fall. I bought them from territorial seeds. This is my first time growing them. When I harvest this year and wish to keep some to replant, should I wait to plant them in the spring?

I just read in their website that I should cut off the flowers as soon as I see them. Also it says to fall plant.

For a while I forgot that I had bought yellow multipliers and thought I bought a walking onion so that's why I let it flower. Then when I flower didn't look like bulbets I started to wonder. Thanks for your help

"Flowering is generally rare in this type of onion. Rare enough that some
of us will never see a flower head in our multipliers. Seed that may
result often germinates poorly and may produce all kinds of different
onions, some of them may be worthwhile to keep and propagate, if you
want to go to the trouble."

I cuncur. Seed from potato onions is rare enough that amateur breeders might be interested in it. Breeder Kelly Winterton has been breaking new ground in that area, and has developed several new potato onion varieties using seed. He has posted a lot of really great potato onion info on his site: Potato onions

There is a lot of interest right now in getting true seed from alliums which are traditionally propagated by vegetative means, which also includes garlic and walking onions. If you do get seed, I hope you will offer it... I could send a few people your way.

I just cut off all the flowers!

The process of saving seed from potato onions is a process of several years. Go ahead and enjoy and learn about what you have. Spring or fall planting really makes very little difference. It sorta boils down to what is most convenient for you. You might get a bit more attempt to flower from fall planting, but even then it will not happen most years.

I have some of Kelly's Green Mountain and a yellow multiplier from Jung's in WIS. I have planted them in both spring and fall, and find very little difference. The fall planted tend to ripen a bit earlier is all. Relatives used to plant a lot of yellow multipliers and they always planted in the spring.

I have very little knowledge about onions, just wanna chip in what I have seen from my personal experience. We had a full raised bed of whites, from seed, and when they sent out the flowers we lost the bulbs. Someone told us that was because it spends its energy on flowering instead of "bulbing"? How right/wrong is that info?

Seeds that's different

I had a yellow onion that had started to go bad. I tossed it in my compost bin (so i thought) it had rolled out and rooted itself in the ground. i was cleaning up that overgrown area and saw what looked to be a long scallion with a big white partially blooming bud on it. still attached to the original onion! i stuck it in my garden and it bloomed. i had never seen or heard of such a thing.