I can't offer you much personal help, but I trust Cooperative Extension folks. Clemson is not too far from you, so this information should be valid in your area:
Gayle, do you mean Verbena bonariensis, sometimes known as Brazilian or tall verbena? If so, when the danger of a hard frost has passed, cut back last year's stems to a low framework. Cut just above any new shoots near the base. (By the way, that is a great plant. I love it tucked here and there through a border.)
Thank you both....Steve G and Douglas Hunt. Not sure about the proper names. This plant was growing in some spreading, low verbena we purchased and the lady at the garden shop asked if I wanted it or should she pull it out. I always love something out of the ordinary so I kept it. It is a tall, willowy plant with purple flowers. I just love it. Thanks for you help!
Perhaps you could post a photo, Gayle. Verbena bonariensis has thin, stiff stems and can be quite tall.