A lush, green carpet of moss is the best way to soften the hard edges of a flagstone walkway, and will give your landscape a rich and welcoming, naturally woodsy appearance. Once the moss is planted, the plants will thrive with virtually no care; as it spreads, it will help to deter weeds and grass from sprouting between your flagstones. Moss is an evergreen plant and will stay green all year.
Purchase moss at a garden store or nursery, or harvest existing moss growing on your property. Moss can often be found in damp places near a faucet or along a building foundation. If you don't have moss, ask a neighbor if they are willing to share. Peel up pieces of moss with a trowel, putty knife or table knife.
Pull any weeds or grass that has grown up between your flagstones. Moisten the soil around the flagstones and the bottoms of the moss. Lay the moss on the soil between the flagstones so the roots make contact with the soil. Alternately, place a piece of cardboard over the moss and step firmly on the cardboard.
Water the moss immediately after planting, and water it every day for three weeks. After that time, the moss won't need water unless it begins to look dry or lighter in color.