I love glories, particularly Grandpa Ott glories. They open in the morning, but by noon, they have closed. Is that because it is so hot here in Florida? The leaves showed some yellowing, and I figured it was from too much watering. But now I'm concerned about the blooms closing so early. What's going on?
That's why they are called morning glories. That will happen any day that is warm/sunny. If it's overcast all day, and especially if it's cool, the blooms may remain open throughout the day, but if the sun is out, expect them to close as soon as it warms up for the day. The yellowing of the leaves is unrelated, and could be one of a number of things.
Morning Glory plants are very sensitive barometers. For the flower to bloom, their internal hydrostatic pressure must exceed the surrounding atmospheric pressure. These plants are pressurized by the atmospheric pressure, which peaks early in the morning, and then it gradually drops throughout the day.
As the day progresses, whilst the surrounding atmospheric pressure is dropping, the plant’s internal hydrostatic pressure is dropping at an even greater rate. The net result is that relative to the atmospheric pressure, the hydrostatic pressure is dropping below the threshold that allows it to burst into full bloom.