I usually have no problem with my sambac, just put it out during warm months and bring it back indoors during winter with some serious cutting back..it has done OK for now.
However, the grand duke, the double whorled variety (Indian sambac) and the pink jasmine (the one you find everywhere now)..they are all happy to grow..just leaves though! My Duke puts out maybe one or tow measly flowers in the summer..then more leaves. Any help/suggestions would be greatly appreciated. I live in Dallas area.
Happy gardening!

I'd use decent-sized clay pots with a big clay saucer, and on hot sunny days water until the saucer is full; it'll likely be dry by evening and the extra evaporation can help keep the plant from wilting. Full sun in the dry South may be too much for it; give it some afternoon shade to prevent sunstroke, my good man!

I still don't know exactly where fertilizer fits in with sambacs; reliable sources say too much and you get more growth and less flowers, but I think this family needs regular feeding, perhaps at half dosage, to keep them full of vim and vigor.

Finally, remember that the Duke, unlike other sambac varieties, is much more seasonal a bloomer, needing the sun, heat and humidity of summer to rouse him to flower.

What we're all trying to do with the sambacs, most especially the Duke, is to restore them to their grand ancestral conditions in the tropics of South Asia. Think steamy jungle. Think monsoons. Think rich, moist soil. And if all that work makes you feel like the butler or the upstairs maid, think of the Empire -- I mean, those flowers!

Good luck!

Jim