You do not say what your problem is! Unless you are saying that your high BP is related to circulation problems. Do you feel the cold? That might give an indication. Anyway ginkgo is supposed to help peripheral blood circulation. How effective it is I don't know. And the head is part of the periphery so that's where the brain comes in.
I'd be surprised if it had a noticeable effect. All that aside, there is at least one herbal medication for high BP available on the net. There are also some excellent databases for herb information. Try doing a search on <A HREF="http://www.***********" TARGET=_blank>www.***********</A> (IMHO the best search engine around) for herbs and high blood pressure - I'm sure you'll come up with something.