Echinocereus viridiflorus: The special thing about this cactus is not only the green flowers, to which it owes its name, but also the fact that it is hardy down to -20°C if you protect it from moisture.
Mine, however, did not recover after only three days of continuous rain during the summer and unfortunately has shuffled off this mortal coil. In memory of this pretty little cactus, I would like to share this photo with you.
Yes, I think it's not uncommon to put a roof over outside cacti in colder climates during autumn/winter. I even consider putting a roof over my hens and chicks, because they are starting to rot every winter here in wet northern Germany...
The roof shouldn't be too small though. It's not just the moisture from above but also the wet soil that's not good for the cacti.
(I hope this comment will get through to you, as we have massive problems with federation at the moment.)
Got it, that makes sense. Ty.