What's causing this black substance to appear on my bougainvillea?

[QuintinBonsai]

Over all it looks healthy, and has many new buds popping everywhere, but I'm concerned about the blackness that's at the base. I know the wood in that area is very soft and mushy. Am I over watering it? I purchased this from someone else so I am unsure as to what the last person used as their soil. It appears to be lava rock, decomposed granite, and akadama.

 

[Nybonsai12]

It's hard to tell by looking at the pics but it could be some sort of rot, especially if it is very soft and mushy. If you scrape it with your finger does it come right off as if it is already rotten? I will say Bougies hate wet feet.

 

[DesertPanda]

It's hard to tell by looking at the pics but it could be some sort of rot, especially if it is very soft and mushy. If you scrape it with your finger does it come right off as if it is already rotten? I will say Bougies hate wet feet.

Agreed on the wet feet. In addition to overwatering causing root damage, sometimes it will cause stem (trunk) damage as well. How often do you water?

 

[nathanbs]

It does just look like moss or moldy from moisture will likely go away if watering is reduced. I think you can treat the mold with some vinegar on a toothbrush carefully Nice tree by the way.

 

[QuintinBonsai]

I water whenever the soil is losing moisture. The black does indeed come easily with my fingers. I'll try to ease off on the watering though. I plan on repotting it this spring, and I'll try the vinegar with a toothbrush thing. Thanks for your help, guys.

 

[namnhi]

Looks like the soil stay wet for too long. Also if you want bougie to flower, you need to keep them on the dry side and plenty of sun.

NN

 

[Jmontee]

I definitely agree that is a water issue. With my bougie I actually let get almost completely dry but before it starts wilting. In the past I have been a little late and it has started wilting so I water and within an hour it is back to normal. If you are not then I would recommend that you keep it outside in full sun, they love it. If it is inside then that could be a cause for the water issue as it will take longer to dry out. Just keep an eye on it outside as that does look like good bonsai soil and so is made to allow for water to not sit for too long on the roots.

Another slight suggestion. IMO the tree might be better served if you bring the leader more towards the right in the last picture. You can build your canopy over the taller main branch and then follow the natural angle of the tree and existing branches to the bottom left branch. Probably angle the right branch down a little too. Don.forget to remove any lower shoots that are part of your design because they will take away energy from the branches above.

It really is.a beautiful tree by the way, nice purchase!