I grow H. 'Jewel' a double, white, scented one with a little red in the throat. The scent is detectable, but certainly not strong and also not especially pleasant - a little musky, moldy to my nose. I have seedlings of H. brasiliensis (or brasilianum, not sure) and H. immaculatum, two of the scented species, but they have never bloomed, so I don't know what they are like.