Something about the ECHINOPS (aka- 'Globe Thistle') flower absolutely drives Bumble-Bees crazy. This ECHINOPS plant is one of the largest flowers in my gardens. Each one of these blue ball-like flowers is about 3+" and there are hundreds of them in this single plant. Granted, it is one of my oldest plants but by the end of the summer- when it is in full bloom- it is about 6' tall and close to 10' wide. It is a monster.

The individual flowers (balls) start out a fairly dark steel blue and lighten up as the season progresses (they are about half way through the season in this image) and most days I cannot even begin to count the number of Bumble-Bees either on or flitting around it.

The photo here was taken mid-afternoon this past August. There were a dozen Bees on this single flower.....a few flew away as I got closer but the guys here seemed completely oblivious to me....and to each other. HEMEROCALIS (aka- 'Daylilies') in the background.