It is most likely to be because they have been too dry. I'm not sure where you are but lots of areas have had hardly any rain and they won't have liked that.

Hi Balcony I 'seem' to remember you are in the south. If you didn't keep your shallots watered during the drought they would have decided that they needed to set seed as they were under stress.

Thanks for your replies! :-))

There is much conflicting info around. I heard from several people that they never water onions after they have been planted. I'd been watering ours till I went to Spain at the end of April then I left them the whole of May without a single drop of water. Then just a week ago I decided that as they weren't fattening up perhaps I ought to water them again & so I did!

I too have some plants bolting and some setting seed also. It seems the early heat and the draught we had are taking there toll.

Yup inevitable really.

So what do I do with them now?

Today, Friday 3rd June, I went down to the allotment & cut off all the flower heads I could find on the Shallots. I didn't find as many as I'd expected - perhaps 8 or 10, I didn't keep count!

I haven't seen any on the Onions from sets or those from seed.