Few moss varieties can withstand full sunlight. Two exceptions, Irish and Scotch moss (Sagina subulata and Sagina subulata ‘Aurea’) can both withstand full sun or partial shade. Their hardiness and adaptability make them invaluable in the home landscape. Irish moss offers a deep, dark green coloration and Scotch moss appears yellowish-green. As perennials, the moss plants come back year and year.
Natives of Europe, Irish and Scotch moss plants are both often referred to as Heath Pearlwort in English, or Mungan Mointich in Gaelic. Irish and Scotch moss can withstand light foot traffic, which makes them favored choices to plant around stepping stones or beside walkways. Exceptionally hardy, they can survive temperatures below 30 degrees Fahrenheit, according to the Washington State University Whatcom County Extension. Irish and Scotch moss are suitable to grow in U.S. Department of Agriculture plant hardiness zones 4 to 9.
Flowering and Dividing
During the spring and early to mid-summer, Scotch moss produces a profusion of petite white flowers. Irish moss also produces abundant white flowers from spring into mid-summer. Both plaints are easily divided in the spring or fall. You dig the plants up, divide them into manageable clumps with your hands and replant in a new location. Each individual moss plant will spread approximately 6 to 12 inches.
Scotch and Irish moss prefer evenly moist soil. The plants don't grow well in waterlogged locations. During times of drought, the plants may die back, but they'll usually spring back to life once irrigation is restored. Highly adaptable, Scotch and Irish moss will tolerate alkaline, acidic or neutral soils. They grow well in sandy loam or clay-based soil. Both types have a moderate growth rate when planted in an ideal location.
Height and Uses
When fully grown, Scotch and Irish moss both stand approximately 6 to 12 inches tall. Their low growth makes them acceptable substitutes for grass in areas that don't sustain excessive foot traffic. They can also be used as filler plants in rock gardens or flower baskets. The plants offer good deer resistance so they can be successfully grown in areas with deer problems. As evergreens, Irish and Scotch moss offer year-round color in any location.