Question
My wife and I have four crape myrtles.  One is a dwarf variety and the other three are larger (7') plants.  All but one have leaves that seem to be half green and the other half brown, like they are dry.  We are watering everyday and do not understand what might be occuring.  Can you shed some light on this problem?  All are planted in full sun with good circulation.

Answer
Bruce,
Is the one that is browning the dwarf? It is unclear from the question. I ask this because many of the dwarf plants that they market are genetically weaker than the improved varieties. Have all the plants been in the ground for more than 5 years? If so then they are outside of the transplant shock time frame.
In any case, there are a few possiblities for the browning. The one plant could be effected by root rot. This occurs when there is poor drainage in one area immediately around the effected plant. Is the effected plant at the bottom of an incline? This is usually an area that will stay moister longer. I would recommend that you cut back on the watering to every other day for 45 minutes to 1 hour duration.
The other possibility is tip blight. This is a disease that will cause the leaves to brown out and die. I would recommend fertilizing them in the fall and spraying them wil a fungicide in the spring that is labeled for tip blight.
If you need further assistance, please let me know.