If you're walking on it, there are bees to consider when it's in bloom. Depending on how tidy you want it to look, you may need to trim the bloom stalks when it's done blooming. Some varieties need trimming more than others, I think. Even the lowest growing will mound up a bit, so that needs to be taken into consideration. I've seen pictures of a few combined varieties used as a "lawn", and they can be quite lovely in bloom. If it's a heavily walked on area, you'll need stepping stones. It can take some stepping on, but probably not constant traffic.
