Debra, you might try contacting Lavender Ridge Farms which is north of Denton and see if they can give info.
http://www.lavenderridgefarms.... Seems like they might know which lavenders do well in your area. A lot of perennials die out after a few seasons. When they look their best, it's usually time to rip them out and start fresh. Lavenders may be more like perennials than shrubs which tend to last longer.
