No, there was no place left in the pot. They're in the ground. Along with all others, they are in a marginally elevated location, so they aren't sitting in a puddle even after heavy rains. As for rock, having read that their presence is considered beneficial, I've been gathering small stones from the garden and placing them among the semps, though so far they're mostly on or near the surface.
They say there will be 5 days without rain starting today... but they made similar claims before.