As for growth habit categories, that's a sticky wicket. I see broad categories, like "tree type", vining, recumbent (creeping), and self-heading. Funny thing is sometimes a viner becomes recumbent when mature (example - Bob See hybrid, vines when young but I have a mature piece in a pot, plant is blooming and growing recumbent, not vining). Examples of true recumbents are P. gloriosum and P. callosum. Self-headers is a tricky category because, perhaps, they should be called "short-stemmed" - when I think of a self-heading plant, I think of something like Sempervivums, Agaves, or other rosette-type plants. As far as I know, there are no true rosette-type philos, but some come close. If they are short-stemmed, that means the internodes (spaces between leaves) are short, but still present. Eventually, they will get a length of stem but you can repot them to restore the self-header look.
