I have known about Night Scented Stock all my life.

I used to grow Night scented stock too, what a good idea to try growing it inside, I might borrow that idea :)

I must say, that's surprising that it gives it's cent indoors at night.But, I'm afraid I have no idea how that works.

I love night scented stock. I usually grow it, but didn't get round to it this year. I'll have to get some seeds :)

Thank you Louisa, Paul and Hywel. The answer must be
scientific because its light until late evening this time of
year, so the scent is not triggered by darkness.

It 'switches on' about 7 p.m. I have just checked it
at 4 a.m. and its still throwing out scent now, but has
'switched off ' at 8 a.m. Must be a continuous 12 hour thing.
Something we wouldnt notice in the outside garden.
Nature is certainly marvellous.

Incredible.

Reporting in June 18th. I had the window open this afternoon. Closed it at 6.30 p.m.
The scent came on at 8.20 p.m. and hour later than when the window was closed all afternoon.
How the adjacent fresh air affects the timing mechanism of these little flowers is completely beyond me.
I have a Dianthus in a pot in the greenhouse. Keeps it scented all summer.

That's a nice idea...I may do that in my new greenhouse to keep it a bit fragrant in there.

Have closed the lounge window at 5 p.m. Will wait and see what time the Night Scented Stock throws out its scent
today. A scientist needs to work on this fascinating
problem, not me.
Should have put it on Gardeners' Questions, might have
had more theories.