Many flowers are attractive to bees, with different types of bee varying in their particular preferences. In particular, long-tongued bumblebees such as Bombus hortorum tend to favour deep flowers, and of course short-tongued bumblebees such as Bombus terrestris prefer shallow flowers. Sometimes short-tongued bees rob deep flowers by biting a hole in the side of the flower so they can reach the nectar.
In general herbs and cottage garden perennials are good, and annual bedding plants are best avoided (because they have been intensively bred and have often lost their rewards or become so mishapen that insects cannot get in to them – also, many have been drenched in insecticides).
Click on the link to read the rest of the article: The best garden flowers for bees : Resources : Goulson Lab : School of Life Sciences : University of Sussex