Alda, the Trailing Lavender is a shrub, with long slender stems. Gets full and spreads to about four feet, but it looks airy and cascades a little. And, yep, it is perennial--mine are at least five years old. The photograph above with the container shows two Lantanas. Doesn't sucker, reseed, or take over other plants that I have noticed. Any stems that do get in the way/grow over-under-around anything I want kept clear, I just cut back the Lantana in that area. They break easily, too, so if I only want to get rid of a few, say around an Iris, I don't have to go get tools.
This photograph of a young plant shows the stems a bit more clearly.