My Four O'Clocks are opening at 7:00 (leaves, California, seeds, home)

[Caladium]

I think I must have planted seeds from California. For some strange reason my Four O'Clocks aren't opening until it's 4:00... on the west coast!

At first I thought they were duds. I planted them in a spot I drive by on my way home from work, usually around 5:00 and until yesterday all I ever saw were leaves. Then yesterday I worked late. Lo and behold there were the flowers--just opening up as I went by at 7:00.

[JQ Public]

It's actually not the time of day that makes them open, but the drop in temperature. It must be a proportionality thing?