I have a big list of all my plants and the cold temperature for them. I'm pretty lucky and it only infrequently drops below 30F here. I found alot of my temperatures at cactus art's website.

Gonna have to agree with alain. Hardiness varies among plants, but not only that, it also declines with humidity.

Out of all the plants that i see here, the opuntia monacathna monstrose and the tephrocactus are the only plants with some level of hardiness below freezing at 0C"-(32F). I use freezing for reference since it is the temp where most tropical succulents (echeveria) and cacti take damage. But bear in mind, there is the fact that bellow 5 C"(40F), some plants will be shocked, or more specifically, there metabolism disrupted....

Again, im not talking about all plants, but all the non hardy ones, like e.trigona.

You may need to post individual photos if you want to know the hardiness and wet tolerance....

The 3 in square black pots in the middle left foreground of the photo will not survive frosts and as mentioned, the trigona. The others should be as advised, better to protect all if you can.

Keep in mind that the soil should be on the dry side if the hardy plants are to endure sub freezing temperatures. Best to shelter them so you are safe regardless.

Oh, thanks to everyone. Of course, these are not marked with names. I have found that with most succulents and cactus when purchased. I don't know any names - just like them. I'll be covering for sure now.
Can't wait to see them grow larger next summer. Thanks for the cactus ID website. Will go there for help with these. This is an awesome website. Carol

Does anyone know the name of the larger cactus in the back right. I would like to see how big both of the cacti in the back will get. Putting either of these in a strawberry pot might not work. Carol

Opunita monacantha monstrose variegata...

The name was listed an eveything.....its not even rare...

The middle two small ones could be Mammillarias and the small one on the left could be a Rebutia.

The left one is a Tephrocactus, possibly T. Articulatus which is hardy to -9°C.

http://www.llifle.com/Encyclopedia/CACTI/Family/Cactaceae/16060/Tephrocactus_articulatus_var._strobiliformis

This is the closest picture I could find. Many Tephrocactus originate from the Andes. Temperatures may drop below freezing at those elevations.

The 2 Mamms are likely good to 30f. That is on my list.

Thanks everyone. I will study this before planting.
Carol

My monocantha survives a slight frost . It is three foot tall and is in a big pot. I normally protect it if the frost is more than a couple of degrees below freezing. Things in small pots are much more tender. I killed my tephrocactus articulatus. It was much larger , But I think that was below 25º and the soul might have been damp. They were in the ground.