Will onion seeds bolt in polytunnel?

[crops in pots]

Hi, I have grown crops in pots in the garden for the last two years and am now very lucky to have an allotment. On said allotment I have inherited a polytunnel 12' x 27', which although needed repair with polytunnel tape has stood up to several gales.

Anyway now i have the allotment I want to grow different things and am unsure of using the poytunnel for growing seed, I know its too cold for toms etc, but what about onion and leek seed. Books I have read seem to suggest that if temp gets too high the seed will bolt, so will the polytunnel get too hot between now and planting out?

I can't guarantee to get everyday to open the door.

[zazen999]

They will be fine. You will be able to plant the onions out in March anyway. And the leeks; you can keep outside or just plant in a corner and move them to their final positions when the potatoes are harvested.

Just a note of warning though - net all your alliums now as we have Allium Leaf Miner here in the East Midlands...fine mesh is what you need.

[Aberdeenplotter]

Your onions in particular will absolutely love it in the polytunnel but do keep it well ventilated.
Some of the best onions are grown in very arid areas in Spain. I have photographs somewhere of Marshall showmaster onions grown from sets, some grown outside and some grown in my tunnel. The onions in the tunnel were more than twice the size of those grown outside.

Watch with leeks though, they will bolt if stressed and very high temperatures combined with lack of water can be a recipe for disaster.