Question
I'm in Houston. Temperature dropped into 40's one or two days only. got the tibouchina grandiflora in pots by pool. Their leaves are all brown now. some leaves are wrinkled up. tinge of green on a few leaves. am i watering it too much (using rainwater and sprinkler sometimes) or should i bring it inside? Their heights are 14-17 inches. how often should i water?

Answer
The weather is changing, and the nights are getting colder, it is times like this that too much moisture in the soil going into the night can become detrimental; the amount of watering you gave them during the Summer months needs to be reined in. Water in the morning and then let them enter the night with drier soil and as little moisture on the leaves as possible to prevent fungal problems from developing. Tropical plants can be stressed very easily when the night temps dip, and react in many ways, often with leaf drop. I am not there to see the whole picture, but from what you say, I would back off the watering anytime after early afternoon and if a frost or freeze is imminent, then by all means, put them out of harms way, by moving them indoors, but only for the night, then move them back out during the warmth of the day.