I live in San Francisco and have a Tibouchina Urvilleana that has a ton of black spots on its bark and leaves. A lot of the leaves are starting to yellow. I water the plant about once a week but have started cutting it back to twice a week. Sun tends to hit the top of the plant but never really shines on the soil. The leaves that do get sun do not seem to have mold on them. The summer's here can be very foggy and cool so that's probably not helping either. I have started to remove all the yellow, moldy leaves, but I'm afraid my tree will be quite bare if I remove all those with black spots on them. I was also afraid I might be damaging it by removing so many leaves. It especially worries me that some of the branches are black. Is there anything I can do to save the plant? Is this a problem that will clear on its own if I cut back the watering? Any help is much appreciated. Thanks!
One thought is that the leaves will not persist on these forever...like a tree (which this probably is in it's native Brazil). Older leaves will have to eventually fall, to be replaced by the newer growth. Even on my large overwintered tibouchina, the lower branches are getting bare as the older leaves senesce...have to do some cutting back if I don't want the leggy look...or just start some new small plants for next year.
