Onions - when will they be ready to harvest?

The onions that I grew from seed this year are still in their growbag and appear to be still growing - how do I know when they are ready to pull up?

 

You should be able to see the bulb fc, are they spring onion sized or bigger? You can eat them at any stage really. They won't swell much more now the weather is cooling down, and in the spring they will put their energies into flowering so I'd start on them now

 

They are Ailsa Craigs - I can see the bulb on a few of them, and they aren't all that big. Ah well, I'll oik them out and use what I can.

Not going to bother with them again.