Southern Magnolia, Magnolia grandiflora, appears to be a hot spot for bee nectar-collecting.
Bees collect both the sweet-scented nectar and the pollen, and so do many other insects. It’s native to the southeast U. S., but is widely planted in the warmer states. It’s slow growing in a full sun spot and takes up a good bit of room both sideways and up–it grows to 120 feet tall. It will flower better in full sun. The shiny, thick leaves are evergreen and the seed pods are interesting, too.
If you have a big space, a Southern magnolia is a good choice. If your space is smaller, consider a Sweetly Magnolia, Magnolia virginiana, also native to the eastern U. S. and very tolerant of wet areas! That might be a selling point alone!