I need some type of shrub – no taller than 3 feet – with roots that will not spread out to far and get into our leach bed.
Need some shrubs to keep people from driving over our leach bed
There is a dwarf butterfly bush if your site has full sun. "Lo and Behold" and "Blue Chip" are two of these hybrids and should be widely available. Fothergilla and New Jersey tea (Ceanothus americanus) are two shrubs that meet your height requirement and are native in much of the eastern half of the US. Groundcover roses top out at 2 ft and need full sun. The "Drift" series is one example. I hope one of these works out for you.