Tiles and Thyme

Here is a close-up of the front tile and thyme feature at Dad's and Alma's house. Square stepping stones have been made into blocks and a small, thyme plant has been placed in the center of each open space. With time, the thyme will spread and grow, creeping toward the concrete squares and filling in the spaces of soil. I'm eager to see this after growth has occured. The question is, will the thyme have to be trimmed back? Or will it control itself and only stay were it is supposed to? Stay tuned!