By Shazziepx
Surrey,
United Kingdom 
I bought a CESTRUM NOCTURNUM Night Blooming Jasmine in late 2018 and kept in my double glazed porch to protect over winter. It only put on 3" in Spring 2019, returned to porch winter 2020. I originally bought this plant for its evening aroma. It has been planted outside again but at last flowers have appeared. Its making a mess as it drops its flowers. Who can solve the mystery, I have been waiting but it has never smelt?
Looking forward to your responses
17 Oct, 2020
Answers
You are not alone - there are quite a few threads on the internet with people saying their Cestrum nocturnum either has no scent, or its very faint and only detectable if you practically put your nose on the plant. Anecdotally, suggestions were, is it actually C. nocturnum or a different Cestrum; that they have more fragrance if they get afternoon sun; that the smell is strong very late at night when you;re likely to be asleep and unaware of it; the scent is more detectable on hot/warm nights; they are more fragrant as they mature. Not sure I believe any of those, so I can only imagine its rather like Philadelphus coronarius, which is supposed to be highly fragrant - many are,but I had one in two different gardens, neither of which had any fragrance at all.
17 Oct, 2020
In my experience, Cestrum nocturnum only releases its fragrance after 8:00 pm, and "locks up" before 5:00 am. The fragrance is stronger in warm, humid nights. Night temps less than 27ยบ are likely to stifle the fragrance.
18 Oct, 2020
Thank you for the info (Bathgate). Sad news for my tropical garden in Croydon. I will take a cutting for winter as it will grow so fast next spring being invasive.
It is a pleasure to belong to this site, I appreciate all of you for your wisdom.
19 Oct, 2020
This is a tropical plant from the Caribbean, Central America & maybe South Florida. This should give you an idea of conditions this plant needs to thrive. Full sun, rich moist soil, lots of space to grow and for the roots to grow out, yet it must be protected from extremes - extreme temperatures extreme salt, and extreme wetness. It does not want to sit in muck, yet needs frequent watering nor does it want to bake in the sun, yet needs 6-8 hours of direct sun.
No plant wants to be moved about in a pot. Whenever you move the plant - it goes through the equivalent of transplant shock and must adjust to the new location - very stressful.
I'm not sure if you can provide the proper conditions this plant needs to thrive. It's out of it's element. Here is a link that might help.
https://homeguides.sfgate.com/nightblooming-jasmine-plant-care-38078.html
17 Oct, 2020