no idea Diane, but last year I had it near my bedroom window and opening the window at night was incredible! i'm guessing lower light levels will be the trigger for the plant to release scent, but isn't it incredible when you think about it!?. i do know that night scented plants are generally moth-pollinated.

Night-scented plants release their perfume in an effort to attract nocturnal insects.

Until the 1950's, scent production in plants was a big mystery. Now scientists have identified nearly 2,000 scent compounds produced by plants. A particular scent can be a concoction of up to 100 compounds.

The part of the plant that releases fragrance depends upon the species. For many flowering plants, the production of odor is not confined to one area, but is spread throughout the outer layer of petals and other parts of the flower. But some flowers, such as orchids, have specialized scent glands called osmophores that ooze liquid scent, which evaporates on contact with the air.

The creation of scent is a balancing act: plants must generate enough smell to induce insects to fertilize their flowers, but not so much that they waste energy and carbon. In fact, for many species, scent emission is not constant; snapdragons decrease scent production 36 hours after pollination.

Great info Bathgate! Thanks.

Thank you Bathgate. Hope Hywel sees this, as he was puzzled. Goy is the best ?
I have copied most of it into my notebook.

That is a very interesting question, Diane, and an equally interesting reply, Bathgate. I know that flowers which produce their scent in the evening are usually pollinated by moths, but I hadn't considered the link between successful pollination and a reduction in the strength of the scent. Such matters are good to reflect on.

That's interesting how plants can design a scent for specific pollinators. It's proof they are living things.