This wild species of Verbena is identified as Rose Vervain
(Verbena canadensis) in Carl Hunter's Wildflowers
of Arkansas book.
You can see Rose Vervain growing along roadsides throughout HSV.
You may even find it growing wild in your yard.
You can also
purchase Verbena/Vervain in nurseries.
Rose Vervain spreads
well without being invasive, grows
well in any kind of soil, and is drought resistant.
It has fragrant blooms from Spring to Fall. The only drawback is that it seems to succumb to some kind of fungus and dies out, but when it does, we just transplant some from elsewhere in the yard.
All of the vervain shown in these pictures have since died out and been replaced with more. To try to combat this die-out, I am now (May 2016) treating them with Bayers 3-In-One for Roses and Gardens. In addition to plant food, it has a fungicide and pesticide.