Scotch moss is not actually moss; it is a perennial plant that only grows to about 1 1/2 inches tall. It is also known as Irish moss and arenaria. It is the perfect plant to grow in small spaces or cracks, such as between paving stones. Scotch moss flowers in the spring with either white or pink flowers and is suitable for Zones 5 to 7.
Sow—or scatter—Scotch moss seeds on the surface of tilled, well-draining soil that is in full sunlight or partial shade. Cover the seeds with a thin layer of peat moss so that birds do not eat the seeds. Lightly water. Plant the seeds in the autumn; however, you can also plant Scotch moss seeds in early spring if there will be at least one more frost. If you are planting the seeds indoors, start the process in early spring. Fill a growing tray with general potting soil and scatter the seeds on top. Place the growing tray in a sunny area that is between 55 and 65 degrees. Water lightly and wait seven weeks for the plants to begin to grow before planting outside. Continue watering lightly every few days, as necessary.
Dig small holes—just enough to cover the roots—if planting Scotch moss plants purchased from the store or from the seeds you planted seven weeks earlier. Plant multiple plants at least 6 inches apart. They will spread and grow to fill in the gaps over the next few seasons. Plant after the last frost.
Cut back Scotch moss once a year if necessary, generally in the fall. Keep the plants watered during the hottest days of the summer, but otherwise, they should grow well without watering.