Rose Petal thyme gets about as high as English thyme, 6 to 8 inches... probably not what you want for stepping stones, although nice along the edge of a path. Even if you get a lot of plugs, I'd suggest propagating them in window box planters (like the dollar store ones) so you have a solid mat to cut into strips and plant (think "sod")... otherwise, you'll spend a whole lot of time weeding until it fills in.
It would help to know how many 12 packs fit into a 1020 nursery flat, in order to judge size. Given the plug size of the plants, I'm wondering a little if it would be better to get these in spring so they have a chance to increase in size before winter. ?
