Question about grafting

This may seem like a silly question, but where do the hibiscus grafters get all the plant bases they graft on to, and what are they? Do they grow a bunch of plain jane hib seedlings themselves for grafting? Can you graft a tropical onto a hardy base? ....sigh...i just think of things sometimes that keep me up at night, hahaha!

Most of the hybridizers and retailers probably grow their own root stock plants, mainly "Pride Of Hankins" hibiscus plants. I would assume they keep reproducing them from cuttings off of their existing plants. They probably just started with a handful of them and then kept multiplying them through cuttings. I don't think you can graft a tropical hibiscus onto a hardy base since a hardy hibiscus dies back to the ground. The wood itself is completely different on the two types of hibiscus.

Thanks so much! So interesting to me~