Question
I have a small aralia tree in the lobby of my hotel and the leaves keep turning yellow whats wrong.

Answer
Jim,

I am guessing that the yellowing is due to low light levels.  How long have you had the aralia, has it been doing this from the beginning?

You might also want to add some fertilization.  Get some Jobs plant spikes.  They are easy to use and will provide supplemental nutrition.  

I hope this helps.

Gary