hybridizing is very possible. Bill Moragne is famous for doing just that. As for how many traits you get from each is a crap shoot plus it will take years to find out what the new hybrid looks like.

One thing im not sure of is if you grafted a large tree onto a dwarf tree rootstock if you would get the benefit of the dwarf like you would in citrus.

Im pretty sure you cant cross plumeria and adenium.

mike

Tetra, many very good breeders are trying to do what you describe, and having limited success at it. Everyone wants the big, vibrant blooms on a dwarf plant! So far, though, they've been able to produce mostly just "compact", not dwarf.

Mike is right, even if you do cross--and it's quite difficult with plumeria to do by hand--then you must wait several years to find out if you're successful. Best to contact someone like Brad's Buds and Blooms for seeds from dwarf varieties. Or wait and see what the next crop of Thai compact or dwarf varieties are and buy some cuttings.

Mike, I don't think grafting onto dwarf stock changes the growth habit of the scion. Probably not advisable, either, to mismatch the root stock and scion. I could be wrong, though.

Typically, crosses within the species (within Plumeria rubra) are easiest.

Interspecific crosses, like Plumeria rubra x Plumeria obtusa, would be much harder.

Intergeneric crosses, like Plumeria rubrum x Adenium obesum would be harder still, if not next to impossible.

I do not know the answer to your question, but just letting you know that you'd be getting deep into plant genetics for a full answer.

I do know that there are already some very dwarf Plumeria rubrum out there. Plants, such as 'Divine', are quite dwarf. Have you checked out some of these?

Unless I misunderstood your intent I would have to say the best bet is to look for a named plant which has all/most/some of the characteristics you are wanting and enjoy it right now.

Unless of course you want to experiment just for the fun of it. In which case good luck with the plumeria alchemy.

crossing plumerias is actually very difficult. The male and female parts are very small and the male parts must be removed without pollinating the female and then new male parts brought in. Many so called crossings are actually injecting water or objects with pollen into the flower which often results in a self pollenation. The next problem is that the plant has a very large number of genes so getting specific traits are a low percentage. The other thing is that you need to have time because it takes years to see results. I still have some plants from a possible cross over a decade ago that have yet to flower. Bill Moragne had some that took 20 years. Also, from 50 seedlings that made it to maturity, I kept 2 (and only one was really unique)- the rest were nothing special. If I had a plantation in Thailand I would try more, but I don't have the space or time to do this. All that was said above is pretty right on with the addition that cutting into the side of a flower and working microscopically in a tiny window up on a flower attached to a mature plant is so difficult. Good luck.