Like other ajugas, this one has a big flush of purple flower spikes in the spring and adds a nice contrast of texture and color to the daffodils and azaleas. It's a tough, drought-resistant ground cover that isn't bothered by deer or rodents. It keeps its leaves through the winter, but it looks especially good (and black!) in October.
For more black plants you might like to add to your garden, take a look at Black Plants: 75 Striking Choices for the Garden.