The best thing for bee health is a wide variety of flowers, covering as many seasons as possible. There is no one favorite, the favorite will be whatever is providing the nectar or pollen they need at that moment. Just to give you some ideas:
Clover (red or white), asters, sunflowers, flowering herbs such as lavender, rosemary, basil (especially perennial basil, but that won’t do well in your climate) and berries, such as raspberry, strawberry and blackberry. The USDA has a map with climates and bee forage sources on it, which Mr Google could find for you. That should also give you some ideas of what to plant for (almost) year-round food for your bees. This is one list for Maryland, but they cover the rest of the US with their maps too:
Here is some natural forage info for Vermont:
Certain flowers really do affect honey flavor. My favorite is lavender flower honey - not the stuff we get in the US, but from hives which are in the middle of acres of lavender flowers in France. Just heaven, and doesn’t taste anything like lavender smells. Orange blossom honey is also lovely. Clover honey is very mild and somewhat nondescript to my palate. Goldenrod honey smells of old sport shoes, but many people like it. So many scents and flavors, you would need a big book to cover them all, and then it is all subjective anyway.