In one of the front driveway beds, they cover the lavender blossoms of Walker's Low Catnip (Nepeta).
In the vegetable garden they buzz loudly all over the blooming late spring chard and kale flowers. The back flower bed is buzzing loudly, too.
There are trees in the front yard crawling with honey bees: The huge catalpa and another tree I have yet to identify. The mystery tree has tiny bell shaped flowers at this time of year. Along the side of the driveway the Sweetspire is also abuzz this week. On the other side, the pink-flowering Black Lace Elderberry is covered with honey bees. This lavender-blue flowering perennial is one I bought 4 years ago at a local nursery. The lable said Heliotrope but it looks a lot like a Verbena. Either way, it is a very agreeable ground cover for the front sidewalk bed. It spreads to cover any bit of bare ground, preventing weeds from coming up. And, it spreads politely not aggressively, slowly moving into open places.
I've shared it with many gardening friends who are also unsure of its name but love the butterflies and honey bees it attracts in early summer.