Our four o'clocks are an old time favorite of ours which we have grown wherever we went. Well, now we have them in Memphis, TN. They are hugh! They have closed blooms by the thousands which will not open. They are like minister's daughter on a prom date!
Why won't my flowers open?
Maybe they don’t know it’s 4 o’clock?
Couldn’t resist a little joke. I don’t know for sure why, but the link below states that they open when the temperature drops and maybe your temp is too high?
http://www.ufseeds.com/How-to-Grow-Four-Oclock-Flowers1.html