T & M heat treated onion sets going to seed

Can i cut off the seed head and eat them as "spring onions" as they have only started to fatten up.

Yes but be quick as the flower stem soon hardens up inside the bulb.  You can pull it out and eat the rest, so all is not lost either way.  They are also good as stir-fry or braised as a side dish.

Mine went a couple of weeks ago and got pulled out and eaten up 

I'm having the same problem with Red Barron sets I planted in March. Like last winter's woody leek and  this spring's hollow rhubarb, I put it all down to a very dry mild winter and spring

.

I have had the same problem with so called heat treated ones in the past bought from Marshall's as well as T&M!

It is the red ones that are the worst.

The old chap on the plot beside mine  got some from Marshall's last year, they almost all bolted, he is the type that knows everything, the rest of us know nothing!

I now buy mine from Wilco, 3 bags this year Turbo and Sturon, £1.99 a net if I remember right, so far there is not a bolter in sight!

Same problem here too.  Every single one of the Red Sun overwintered sets have put up a seed head, plus 2 or 3 of the white Shakespeare sets.  So far the Longor shallots are all OK.

I guess that I should be happy!! that only one of my shallots has bolted, all the onions and the rest of the shallots seem okay, (atm!). Only planted in the Spring though. arh.

Ordinary onion sets are produced by planting seed late in the Summer so that only small bulbs are produced. At lifting the bulbs have not initiated a flower. That is the theory, but some of the bulbs do not keep to the rules and have an embryo flower waiting to grow when planted in the Spring. Bigger sets are presumably more likely to bolt.

Heat treated onion sets are kept at 25 degrees C for about 3 months. That kills any embryo flower so that they do not bolt. The odd one may escape but I would suggest that if as many as half of heat treated sets have bolted the heat treatment process has not been done properly. I would take a photo and attach it to an email of complaint to the supplier.

Well done. That will buy a big bag of onions.