Marica,

Not sure I would call it a hybrid, with grafting.

The Arabicums, Swazicums are known to be more tolerant of cool conditions, but cool and wet are not good.

Probably best to graft obesum x obesum. Problem you will have with grafting different species/variants is that one will grow completely different than the other in most cases. For example: if you graft a obesum onto a arabicum. The obesum will probably grow faster than the arabicum are look odd. This is not always the case, but you can achieve the same with obesums and have caudex and bloom both.

Rick