Japanese Onions Bolting

[Jonnyt]

Nearly every one I've grown from seed has now bolted. I've been watering them through the dry spell. Any ideas why these have bolted?

[ameno]

The usual reason is that you started them too early.
Onions are biennial, so they naturally grow one year then flower the next. This means that if you start the plants too early, and thus the plants grow too large before winter, they are likely to bolt the following spring.

[quanglewangle]

If I understand the term Japanese Onions correctly they are onions meant to be started in the autumn and stand over the winter to get a head start in the spring and mature early.

I grow them every year like this with zero bolting. But I do grow from sets, not seed.

Edit I start mine 2nd week of October