I really want a large cactus. What is a fast growing columnar cactus that I could get my hands on?
Austocylindropuntia subulata is a good one. But may grow TOO fast :O
Lemaireocereus marginatus is a good one too. (One of my favorites)
also Celiostocactus strausii (probably all cleistos are good, but i only have experience with 3)
Stetsonia coryne is fantastic, likes full sun, and has maybe 4 inch spines.
Polaskia chichipe is a good one too
One that may take a bit longer, just is much more beautiful are the brazilian cacti, Pilocereus. They love sun but despise cold
I think all of those can be found in big box stores
Cleistocactus can definitely be fast-growing, but many species are rather sprawling, instead of perfectly columnar.
However, as Microthrix mentions, C. strausii is a good columnar species, as is C. hyalacanthus.
Cereus peruvianus is so fast, I have to pare it down every year.
Thanks for the suggestions!