It is hard to get moss to grow on cement, even in shade, which moss needs. But if your balcony is in shade and you want to create a mossy environment, consider using plants in terra cotta pots all around. You can go out, find some moss, put it in a blender with buttermilk and give it one quick whir of 10 seconds or so. Paint it on the pots and keep them evenly moist with interior watering and spraying, until moss is established.
