Thanks zuzu! The bloom photo at that site shows a definite yellow shade where Ipomoea alba is a totally white bloom, so it probably is a hybrid. I can't get back to their page now because a window keeps popping up saying something about a security warning and insecure connection but when I typed Evening Glory into their search box, it brought up a page with photo's of both the white Ipomoea alba and 'Evening Glory' with the yellow bands.
