Propagating cestrum nocturnum is not difficult.
Quite often, cuttings of cestrum nocturnum will root if simply placed in a glass of water. Ideally, for this you want to snip off a longish branch from the parent shrub – perhaps up to 18″ long – and place in a container of water in a sunny or bright situation.
Roots take some time to form, so change the water often.
It is nice if you cut off a flowering branch, because then you can enjoy the perfume of the flowers indoors during the evening while you await the roots forming.
Cestrum nocturnum tends to throw out roots eventually whether or not the cutting is young (this years growth) or woody (last year’s growth).
If you prefer, you can take a much shorter cutting and place in compost filled pot. Water well and seal inside a plastic bag, and keep in a light and warm position until you see signs of new growth.
Remove from bag, water well and place pot on a saucer or other container to catch the drips. Pot on when you see signs of the roots appearing through the bottom of the pot.