[joseph]

It seems to me that the onions were planted unseasonably... Onion flowering is typically due in my garden to getting cold after they reach a threshold size (somewhere around pencil sized). That can also trigger onions splitting into many small plants instead of one large bulb. My recommendation for next time would be to research when and how onions are typically planted by your neighbors. Seeds/sets/plants? What season?

In my climate raised beds are very susceptible to dehydration which can also trigger premature flowering.

Once they start flowering I don't expect them to grow a large bulb. So I figure harvest them whenever you'd like...