Nectar ? Which flowers have the most in Wisconsin?

[Dr. B in Wisconsin]

Hello
This is my first year being a beek. The year is winding down very quickly here in Wisconsin. I took a short bike ride to see what was left on the edge of town. I saw lots of white asters with my bees on them, ( I know all my bees by name) My question is those asters are quite small although there were quite a few. Is there much nectar on them and how do asters rank with other flowers.
Thanks for any answers.
Brian

[danno]

I'm across the lake so things should be close.  Our best is star thistle.  When the weather cooperates they last for several weeks.  This year we had a pounding rain about 1 week after they flowered that washed them out.  After that we have goldenrod then aster.  Goldenrod smells and aster crystalizes really fast so I pull just before the goldenrod starts.