My Heavenly Blue Morning Glory was pruned last week just as it began to bloom. Today is September 1. What can I do to save the blooming season?
Depending on where you are located, your first frost will be anytime from now till mid-November. In any case, This is an annual morning glory, so it will do it's best to flower and go to seed before frost kills it. These plants sense seasonal changes by day-length, temperature changes, and a couple other things. These things tell the plant Fall is coming, and they don't have much time left to live, so they will grow quickly, and put out as many flowers as possible.
Things you can do to extend the season are:
And it will depend partly also on how far back it was pruned. If it was cut back less than 1/3, that's the best case, and you should get flowers again in a couple weeks. If it was cut back by 1/2 or more, it is going to try to regrow that before flowering much, so if that's the case, don't expect too much from them. But as I said before, flowering is a high priority now for the plant, so don't lose hope.