[Plot 6B]

Do they not serve the same purpose at this time of year?
Any thoughts?

[mumofstig]

I think it is easier to progressively  harden things off in a cold frame. Put plants in with top on, open top a little during the day, then ditto during the night, until the top is fully open, day and night and plants are hardened off.

In a greenhouse all you can do is gradually open the door, but even then plants are still very protected inside.

[New shoot]

The polycarbonate lid on my cold frame broke a couple of years ago, so I now have a small panel from an old chicken run topping it.

If it is really cold, I put a solid lid of a couple of panes of greenhouse glass on top of the weldmesh panel.  Otherwise it may get some fleece draped over at night.  Most of the time it just has the weldmesh top.

I find it ideal for hardening off.  The sides protect from the worst of the wind, but it is way less protected than the greenhouse.  All my onions, leeks, greens and herbs have been through it so far.