I think if it isn't the predominant source of pollen it may not be a problem.
You may want to look through this PDF. It contains a bunch of information on the CA buckeye.
http://www.diablobees.org/downloads/CA_Beekeeping_V2.pdf
Thanks looks like some reading for tonight. I'm in the process of transplanting tomatoes before the rain come in. And it's close. Neighbor just told me he wants to do bees between our posting.