2) It is hardy almost anywhere (provided it has drainage, of course, and lots of sun): I know it is being grown all over southern Canada, the Northeastern and midwestern USA and all across this great country of ours (it is Fourth of July after all today)...not to mention Europe.
3) It propagates like a schmoo (if you do not know what a schmoo is I feel sorry for you).
4) It is listed as Threatened on the Federal Endangered list (only a few thousand individuals are known in its limited range inside Carlsbad Caverns National Park)...I am sure more plants of this are growing in Denver area gardens nowadays than in all the wild! And who knows how many in gardens around the world...a good example of why cultivating a plant probably aids in its conservation: no need to ever recollect this when it is so widely known and grown, and people now have a living reminder of how important preserving a wild plant must be.
5) Yes, it has spines, but they are of the wimpiest kind: you could easily toss this back and forth and not hurt yourself nor your fellow tosser. A rather gruesome image, actually (do please propagate it when you are done tossing).
This is a clump at Denver Botanic Gardens last year: this was propagated from a piece of a plant that had been despoiled by a visitor (one of the very few plants ever to have been so vandalized): the central portion of a large clump had been pulled up, but the surrounding pieces remained: I decided to propagate these and put them all over the garden--this was perhaps fifteen, maybe 20 years ago. And they have gone on to spread and cluster....Interestingly enough, this was also one of the very few plants ever stolen at the Gardens on Kendrick Lake. Hey nurserymen friends: if people are stealing these little hummers, maybe that means you should propagate and sell them?
High Country Gardens sells this mail order (it's amazing more nurseries don't), and in the Denver area you can always find a large assortment of this at Timberline Gardens--Kelly Grummons has actually grown this from seed and selected an especially tiny form which he really needs to name--it is distinctive, and if possible, even cuter!
There are a few cacti that are even smaller in Mexico and South America. There are cacti with far more spectacular flowers. But I doubt that there are any that have so many stellar attributes at one time....I really think this is a cactus that anyone and everyone in America should know and grow. (P.S. it thrives on a windowsill--you don't even have to grow it in a succulent trough. But shouldn't everyone have a few troughs full of hardy succulents?)...
I have proposed this several times to the Plant Select committee, and I am always rebuffed ("too small", "too weird", "too esoteric", "too different"). I think they are dead wrong, don't you?