Those look like Four-O-Clocks. (See link) I like them, they have a wonderful fragrance, in fact I wish I could find a perfume with that fragrance in it. But a lot of people hate the plant because it is considered invasive. I just pull it up if I don't want it. It comes in a lot of different colors.

Here is a link that might be useful: Four-O-Clocks

The link's author says the flowers open when stimulated by the fall of temperature as night approaches, say, 6 o'clock. How does that work out in FL? Is there enough temperature drop on a usual dry summer day/night to open?

Four O'clocks are evening plants in FL. They do open up but put them where you would see them at night. I love them but if you plant them in the ground they will get enormous tubers and they spread, so a pot is really best for these.

They drop loads of viable seed(which is likely where yours came from) - so even in a pot you need to be vigilant to avoid an invasion...

My four o'clocks usually open between 15.00 and 17.00 and stay open all night, even in the middle of summer. If I am not getting many flowers during the high heat months, July & August, it is usually because I am not keeping the moisture level consistent. I like to keep them near windows so the scent wafts indoors in the evening. Supposedly some people are unable to smell their scent, and some plants are more scented than others. In my experience, the fuschia-coloured ones have the most scent.

They die back completely at some point during the winter, but come back as soon as it starts warming up. I usually have last year's seeds sprouting about a month before old stock pokes its head out of the ground. Old stock quickly catches up in size and are typically larger, more robust plants than first-year plants. If you have more than one colour growing, they tend to cross readily which often results in new plants eventually being all the same colour. Fuschia seems to be dominant, but I had some salmon ones from crossed fuschia and whites that stayed stable for several years. They will sometimes produce multi-coloured blooms when crossed or even different coloured solids on a single plant. The multi-coloured ones eventually produce solid colours, in my experience.

Leekle, you were going to try some in sunken pots in March. Did you go for it? How are they doing so far? You should have bloomers by now. And I hope they are behaving for you. :)

Carol in Jacksonville

Here is a link that might be useful: Four O'Clocks - March 2014 thread