Is there two forms of the Monstrose? I was reading there is a large and dwarf variety, the pictures I saw show a lighter green sort of hairy one, and the large dark green monstrose. But I have found a lot of online info incorrect before of course...
Anyway i seem to have one of each, a small arm of the darker one off a large plant and then a small light green one, is the latter just a baby that will grow, or actually a dwarf?

I've often wondered this myself. At the very least, there are two distinct Cereus monstrose forms - I suspect they are actually clones rather than seed-grown - commonly in circulation, although whether they are both Cereus peruvianus is a bit questionable. From what I can tell, the dwarf form is either a relatively recent cultivar or really short lived as I have only ever seen very small and presumably quite young specimens, whereas I have seen some very large and much older examples of the large form.

I personally doubt that the dwarf plants that we see so often are related at all to the original Cereus peruvianus.

Ok down at Collector's Corner (which very unfortuantely for my wallet I live around the corner from) they sell both forms as Cereus Peruvianis, I can see a colour difference in the smaller plants. This one I have here that came in a bulk lot I bought I assume is a 'dwarf'


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Anyhoo I think I'll be safer buying large cuttings off a Daddy plant rather than trying to grow a small one for the garden