The end of March, but I have put some in a large trough already to get a longer crop period.

mine seen to bolt every year im pretty dismayed i water well but all my veg bolt early ??

Bolting seems to happen when you disturb the roots. The onion bulb reacts to the disturbed roots [thinking they are starving] and tries to set seed. Try and leave the onions undisturbed and cut off any stalks trying to appear. My biggest problem is trying to stop the drying stored onions from blue-gray rot.

I'd certainly wait until the end of March as you are in Yorkshire Steve.

Kildermorie are you hanging the onions in a cool, dry, airy space? We had very little rot this last year and only finished to crop a couple of weeks ago having given two plaits of onions away.

Our problem was that even having dried our red onions very carefully and hung them in a cool(ish) cellar, they sprouted very exuberantly, and by Christmas we couldn't use any of them.
Our red, yellow and white onion sets are all ready to go into the prepared bed in about a fortnight's time.

I always plant my onion sets in the autumn - they look after themselves in the winter and ... no bolting. If you water onions once a week or fortnightly or whatever, then you need to keep on doing it. If the cycle is interrupted, onions will bolt, especially in warmer weather. This is another reason to plant salads like rocket, early and late, but not in high summer, as they bolt very quickly.

If you planted onion sets in most of Scotland in autumn they would simply rot, as do broad beans...

Our autumn planted ones disappeared almost without trace - could it have been mice?

Quite possible Gattina or the very cold weather you get.

Good point, MG, seeing the number of cats we have, cold weather is more likely, I suppose.

Thanks everyone I met my new allotment neighbour yesterday and he tends to put his in late March early April due to the site being exposed to the elements.

The best advice you can get in your early days on the allotment is going to be from your fellow allotment holders. They will have a knowledge of what works and what doesn't having tried things out over the years. I'm not saying that we GoYers can't offer advice but there is nothing like speaking to the people working the allotments next to you.

Hello! Onion sets planted every autumn, including last bad winter of 2010/2011 when temps got down to -17C for several days, had no effect whatsover on my autumn onion/garlic crop, and I am just finishing off the last few, harvested last sumer, now. I had one group that was disturbed by cats and did not grow at all. Cats, and not temperature was/is the problem. I can understand about rot with the rain in scotland. The simple solution is to sheet the onions when rain is excessively persistant - very easy to do! Stops the rot and the bolt!!

Ankq that is good news and... in the 2010 - 11 winter we had temperature below -17˚C for months at a time. The bulbs just rot and die! If it works for you great... no gardener or allotment grower up her will plant onion sets or sow broad bean or pea seed in autumn, they've all discovered it is a waste of time effort and energy! Not to mention they have to go and buy the seeds/sets again!

I shan't ever bother with autumn onion or broad bean plantings again - waste of money and effort. We've had temperatures down to -22° this winter, but for no more than a few days. It's enough to kill most things that you REALLY wanted to keep in a garden , even in a greenhouse or against a house wall. The weight of snow tends to finish things off.

Thank you Moongrowe and Gattina ... I am feeling very smug living in Worcester!! :-)))) The bees are humming in the damson and prunus trees, and blackthorn is in flower ... lovely!

Well, I've nearly caught up with you, Avkq, the onion sets are planted, (ALL the neighbours have been out planting them) the prunus is in flower, we have bees, butterflies AND lizards! It's amazing what just a week or so of warmer weather can do - there were sheets of flowers under all the snow, and everything changes in a flash. We aren't uncrossing our fingers yet, though.