After getting rid of weeds there. Pour butter milk on the rocks and sprinkle with crumbled up moss!
This is the recipe I used:
Moss recipe:
1. Put a handful of the moss you want to grow into a blender.
2. Add 1/2 tsp. sugar (or 1 Tbsp. corn syrup) and one can of beer (the cheapest brand). You can substitute buttermilk for beer if you want.
3. Blend just long enough to mix the ingredients and break down the moss.
4. Spread the soupy mixture with a spatula over the ground or rocks where you want the moss to grow.