Why the flower of mirabilis jalapa is called 4o'clock plant?

Question

Why the flower of mirabilis jalapa is called 4o'clock plant?

Answer 1

I think it is for the fairly uninteresting reason that the flower of this plant opens in the afternoon, say around 4 o'clock.

Here is a link to confirm that - http://en.wikipedia.org/wiki/Mirabilis_j...

Answer 2

This flower is pollinated by hawkmoths (Hyles genus) that only come out at dusk so the flower only opens when its pollinators become active. Hence the name for the plant follows its twilight activity.

The long tube of the flower is suited to long tongued, nectar feeding, night flying pollinators like moths. Moth flowers are often pale and most are very fragrant to attract over long distances. Many are crepuscular, opening only with the  fading light. Besides 4'oclocks there are the evening primroses (Oenothera), and even nocturnal opening daylilies

http://readingeagle.com/article.aspx?id=...

The flowers are triggered by evenings drop in temperature to release nectar and a moth attractive scent as long as the drop does not get to cold. Between 13 -21C they can produce nectar. This temperature tie has co-evolved because the moths are active then. If the temperatures fall below 13C the moths are to cold to fly and the plant must self pollinate.

http://www.jstor.org/pss/2388358

http://www.jstor.org/pss/13558

http://www.sciencedirect.com/science?_ob...

http://www.botgard.ucla.edu/html/membgne...