[chili]

have some onions growing under cover majority of them are just waking up and starting to grow however 1 of the blighters has green shoots about 8" long already, would it be ok to trim them back?

[zazen999]

I wouldn't! Just leave them be.

[JaK]

No don't give it a haircut. Let it grow, it should be fine over winter.

[prakash_mib]

what variety are they? if they are over wintering, they dont need to be under cover. They always plan their growth in a remarkable way.
they dont need any mollycoddling at all (DD's line to me last year) 

[chili]

i put a cover over them because some bird/rodent pulled a few up shortly after i planted them

[prakash_mib]

onions do pull out themselves for various reasons. birds help them too.
onion sets when put in ground immediately thrusts out root. and when there is a little bit of resistence from the soil it pushes out (not theory. I saw this in my back garden on spring onion sets under cloch)
frost/earth subsistence make it fall out of its place. Just plonk them in and they will be allright. we do this once 3-4 days at start and then forget about it once they are settled.
putting cover will affect their behaviour for the coming long winter (if it is a hard one)

[zazen999]

Not theory at all Prakash - fact!!!

I never believed the bird theory - I'll stick the the onion root fact personally, as they even do this if you pop sets into modules.