You know Carter, I am not really sure. There are so many Arabicum & Thai Soco's and most being hybrids of both or through crossing. I believe that the Dwarf is just a form that was produced and trying to create a "new" hybrid. It is really becoming so conveluded w all the different ones available.
PNW is an older hybrid.
This one has grown taller, because I neglected to get it potted up into a wider pot.
Rick
