I have planted a variety of onions and scallions in a raised bed, the tips of some are going yellow, plus some bulbs are coming out of the earth. I pulled a few yesterday and it looks as though, if I leave the rest any longer the stem will grow even bigger and grow down into the bulb if that makes sense? Jopefully you can see what I mean from the photo. Does this mean they are going to seed/bolted, I should take everything out of the ground now, or am I already too late to store? Any tips to stop it happening next year?
If the onion plants go to flower, the flower is clearly visible rising from the bulb.
The onions in the photo are 'thick-necks', probably not flowering, but a phenomenon caused by overly rich soil, possibly too much organic material high in nitrogen. These will not keep well and need to be used.
Leave in place any that look like forming a good bulb, and store them.
Try to balance off in future years with some potash which counteracts the nitrogen, which will tend to decrease anyway unless you add more.