Recently I participated in the Annual Spring Piedmont National Wildlife Refuge/Rum Creek Wildlife Management Area Butterfly Count. All of the participants I have talked to since the count have told me that they found more butterflies on a wildflower known as Heal-All (Prunella vulgaris) than any other plant.
The plant is also known by a number of other names such as prunella, carpenter’s herb, woundwort, heart-of-the-earth, and self heal. 
Heal-all has long been recognized as a nectar plant used by butterflies, bees and other nectar feeders. However, many books dedicated to attracting butterflies either do not mention it at all, or, if they do, provide little information pertaining to the plant.
Depending on whom you talk to heal-all either is a native or naturalized plant in Georgia. However, at least three varieties of heal-all grow in Georgia.
During the count, we found the plant growing in sunny (the plant will also grow in partial shade) areas along roadsides, disturbed sites, and small unmowed tracts. In most cases, the plants were growing in dry soil.
In spite of its value as a nectar source, it is rarely planted in gardens. In years past, this was not the case. Back in the day, the plant was grown more as a medicinal plant that for its small, showy lavender flowers.
Blossoms appear on thick cylindrical spikes. The plant’s square stem-bearing flowers typically reach a height of a foot or more. The plants we encountered are now in full bloom. Deadheading the blossoms will extend the plant’s blooming period.
Those gardeners that utilize the plant for butterflies often incorporate it in natural gardens or use it in borders. Heal-all can even be grown in larger containers.
Plants can be divided in spring or grown from seed. If you want to prevent them from seeding, cut off the flower heads before they produce seeds.
After you become acquainted with heal-all, you can see why I feel it is an underrated nectar plant.