[rowlandwells]

as the subject suggests we are turning our overwintered onions in pots out of the greenhouse to the cold frame prior to planting the onions have been growing quite well and have long leaves Q. is can i cut the tops back because they will get damaged when there planted out if so  how much could i cut them back before planting out 

[Didiaskew]

What variety are they? The overwintering varieties I've grown in the past have been outside, if they're an overwintering type like Japanese just plant them out they'll be fine if not I'm not sure to be honest I've never tried.

[sunshineband]

I wouldn't cut the tops back unless the leaves are badly torn, as they need them for photosynthesis. Once they are outside, the new leaves will grow much stronger and stand up just fine.

Depends how many plants you are talking about but if it is just a few, you can add a short cane and a soft wire hoop for each, to keep them up for now