Question
I have a potted (20gal) black bamboo all the leaves are turning yellow from the tips back even the new ones.It is outside in central florida  

Answer
Tom,

I am in northern Indiana and have no experience with black bamboo. I suspect you have a root problem, such as the plant being rootbound or the roots could be rotting from overwatering. I don't know because I can't be there to look at it.  Below is a website for a bamboo company in Florida. I suggest that you contact them for help.

http://www.lewisbamboo.com/pblack.html

Sorry I couldn't help you more.

Darlene