I can't move mountains or even small stones. Divide your lilies into small clumps. Using a poacher's spade a long thin bladed shovel. Work it through the stones by rocking it back and forth and into the soil to the depth you need. Fill the hole with compost and scape the pebbles back into place. That how I weed large weeds out of my gravel car park and driveway. Best And Happy Yardening, Nancy.