[HartleyMBaldwin]

they will just sit waiting for long northern days before fully bulbing.

That might have been why our onions sometimes didn't bulb in other years. Although even here, the longest days are light for 15 hours or more.

[metmom]

There’s also a difference between long day onions and short day onions.

Here in the north, we do long day, but apparently they won
t bulb if the days don’t get long enough. Just what I’ve heard, not based on experinece.