And keep it mind that it depends on the year. Some "major" plants don't deliver every year because they are alternate (or longer cycle for some trees) blooming. And some years a particular plant will be seriously affected by weather - even weather that happened months, or even a year ago. In addition, the array/menu of available blossoms varies by location so when bees can't get get their favorite source, they default to other ones that would otherwise be considered "minor" sources. Also small stands, or individual (non-tree) plants, of even "major" sources may not attract attention of the bees. They have a high energy investment in their search efforts so they might pass up an otherwise attractive nectar or pollen source that's too small in number, in favor of a lesser source in great abundance.
I am a horticultirist by trade and a good deal of the info that I've seen on the net is pretty useless. It seems that someone, some time, somewhere saw bees on a particular plant, so it becomes described online as a honey plant.
There is I believe a really good, though older, book on bee forage plants. I haven't tracked it down, yet.