Moss will grow on most any poor soils and rocks if it is in a shady area with plenty of moisture. Moss is found for propagation in similar areas. The thick green ground cover will add to the landscape on a patio as a cool, out-of-the-hot-summer-sun sitting area. Maintenance for the moss-covered stone patio will be minimal--perhaps only a light misting of water periodically during the summer season.
Place 2 cups of crushed green moss into the blender. Add 2 cups of water and 1 cup of buttermilk. Blend all ingredients into a slurry paste. You may need more or less of this mixture depending on the amount of area to be covered.
Apply a thin layer, 1/8 inch thick to ¼ inch thick, of the slurry paste between the stones on the patio. Use your fingers to apply the slurry paste. If possible, gently work the paste into small crevices in the stones as well. Best results will come from where the moss slurry is in contact with some soil and areas that can hold moisture.
Use the misting attachment on the garden hose and mist the moss slurry on a daily basis. The moss must be kept moist in order to become established.
Allow up to three to four weeks for the moss to become firmly established. The greater the moisture on the stone patio, the more the moss will begin its migration over the top of the stones. Direct sunlight will inhibit most moss growth as will as extremely hot and dry weather.