Something to keep in mind, scent is subjective. Different people can have vastly different interpretations of what something smells like and whether or not it is pleasant. Also, fragrance can be highly variable, even within a species. One specimen may be fragrant while others are not. Two specimens of the same species may have different scents from one another. The flowers may not be fragrant at all except at mid-day, or the scent may change a bit throughout the day. One issue with slippers when it comes to fragrance is that, historically speaking, breeders tend to focus almost entirely on visual aesthetics and neglect fragrance almost entirely. This means many species and hybrids that would or could typically be fragrant simply aren't.
As for the Paphs you asked about, here's my take:
- Paph. delenatii - Most say rose-like and citrusy. I find the scent to be more similar to southern magnolia than rose, but not everyone has had the pleasure of smelling southern magnolia blooms, so I think citrusy-rose is a fair comparison. Not all delenatii are fragrant, and strength ranges from faint to noticeable if your nose is in close proximity.
- Paph. malipoense - Variable and hard to describe. Some say pine, others say fruity & sweet, raspberry, candy-like. Some are non-fragrant, but most are at least slightly fragrant. This applies to P. jackii as well.
- Paph. concolor - Vomit and apple peels. I find it to be gross. Fortunately, you have to stick your nose up to the flower to smell it for the most part.
- Paph. Lynleigh Koopwitz - Usually very similar scent as P. maliopense, maybe a bit sweeter and more candy-like.
- Paph. Norito Hasegawa - Never found any NH to be fragrant, though I suspect fragrant clones would be similar to P. malipoense.
As others have alluded to, there are other fragrant species, though many are only faintly so which may explain why you don't read or hear about them much (other than Paph. hangianum). This probably isn't a complete list, just the ones that came to mind as I was writing.
- Paph. hangianum - This is the most fragrant Paph, approaching "Cattleya" level fragrance and as far as I'm aware, pretty much all of them are fragrant. The fragrance usually carries through to its hybrids, with Paph. Shun-Fa Golden being one of the best and most fragrant. The scent has citrusy notes, mostly reminds me of something you'd expect a pleasantly scented cleaning product to smell like.
- Paph. emersonii - This one is hit or miss. I've not smelled a fragrant one, but I have smelled its fragrance via hybrids (s.a. P. Joyce Hasegawa and P. Franz Glanz). I'm drawing a blank on how to describe it, sort of oily floral, perhaps. Definitely pleasant. Hopefully someone has a better description.
- Paph. thaianum - The scent is said to be citrusy-lime. I find it's very similar to P. delenatii. The scent comes through in hybrids like P. QF Mini.
- Paph. primulinum - I find the smell to be a sweet fermentation smell, a bit like sourdough bread yeast but I've heard lots of other descriptions some of which are vastly different than my interpretation. The scent sometimes appears in hybrids as well. Many modern "primulinums" aren't fragrant, but I also suspect many modern "primulinums" are actually hybrids.
- Paph. kolopakingii - Some say urine, some say sweat. I think it's a bit of both, though I'll mention that there are some floral notes in there.
- Paph. rothschildianum - Usually described as peppery, as in black pepper. I think that's appropriate.
I'll add that I've read and heard that many members of the Brachy group are fragrant, though it seems that most are described as foul smelling. Additionally, I think sometimes P. lowii can be fragrant. It sounds strange, but I have a plant that some years I detect a faint, generic floral scent when I check, other years I get nothing.
And finally, gotta give some love to the other slipper orchid genera. Depending on which taxonomist you subscribe to, there are a couple or perhaps several fragrant Phragmipedium species. The most fragrant is Phrag. schlimii, which reminds me of rose perfume. Many of its hybrids are also scented. Phrag. humboldtii has a weird sweat/urine with floral notes fragrance similar to Paph. kolopakingii and some of its hybrids will have the scent as well. I'm not as versed on Cypripediums, but I know at least some of those species are fragrant. Cypripedium parviflorum is one I've had first hand experience with and I can say that it had a nice, generic floral scent.
Anyway, sorry for the novella, but as you might be able to guess fragrant slipper orchids are kind of my cup o' tea.
hangianum smells like cotton candy.... rothschildianum smells like black pepper....
