It is an old-fashioned plant, so only recently coming back into gardens. The flowers are surrounded by leaves that join in the hurrah of color the flower has. The flower has all the look of being an aberation of the leaves that nestle it. Its neat, upright habit in the photo above bely the branches' sprawling, haphazard habit. The treat is that each branch is topped with one of these candy-like, deep-deep purple flowers, as in the photo below.
I try to save seed from the flowers each year. If they drop before I succeed in doing that, I buy them. The seed are hard to find, but more nurseries are carrying them. Often they will self-seed where I least expect it. But I love these surprises of nature and am each year glad to see them in my spring garden.