I would suggest that you try Italian toadflax Cymbalaria pallida
http://www.plantify.co.uk/Cymb...
I have this lovely spreading plants in a lava rock bed where í had also planted Some primulas and other smaller plants. But theItalian toadflax crawls over almost everything I put there. Í have a small garden so í decided to remove the toadflax but I gave up. Next spring I'm going to remove all the other plants. I have not tried to walk on it but it is very hardy here and í can't kill it except to use herbicide. The Italian toadflax is very beautiful with small blue/grey leaves and violet flowers. It is in bloom almost all summer, it is very low growing. It grows in half shade / shade. Allthough it crawls all over this lavarock bed like crazy it does not grow into the grass below this bed. If í can find photos to show you I will post them here.
