I think it is opuntia cochenillifera. I hope I have the spelling right. It is tender at about 20. Mine died that I just planted at 12 degree (BAAAAAAD winter). Its 10' tall parent turned to mush but I see pads forming on the remaining stubs. It is now 5'. We shouldn't have a winter like this for another 20 years. They are good eating also

Here is a link that might be useful: Opuntia cochenillifera

Thanks so much Wantonamara! I've wondered about it for two years. I better protect it if the temps get down. I'm going to try eating some of it too.