Cold-hardy cacti are generally small. Some forms of cold-hardy Opuntia and Echinocereus triglochidiatus can reach a height of about 1 meter. Cylindropuntia imbricata can become taller, up to 3 meters, but I do not know if that applies to the cold-hardy forms, most I have heard of have been about half that height.

Note that the cold-hardiness depends much on the moisture levels too, and it is not enough to choose a particular species, some forms/clones are much hardier than other.

Hello,

The tallest plants in my hardy patch are:

O. imbricata, it's about 2.5'. My shade structure fell on it last winter so it is a little stunted now. There is one in Reno growing against a south-facing brick wall and it is quite a bit taller.

O. phaeacantha because the pads are large. But I have to get into my beds and clean them out. This plant is dying out on me. (good riddance it's like a weed and took over 2 of my cacti beds).

At my old house I had some kind of Trichocereus (not a hybrid) that lasted several years, but I think I finally just took it out because the weeds were growing through the stems.

I live in the high desert though, so my conditions are very different than yours. The plants stay very dry in the winter. We only get about 7" of moisture all year. We had more in the form of snow this year so maybe that's why the O. phaeacantha's are not doing well and that's definitely why the shade structure collapsed.

DZ

Thanks for the suggestions. I swear I've seen a tall cactus growing in southern Ohio along side a house...