Irish moss (Sagina subulata) is not actually a moss but a trailing evergreen that is grown as a ground cover. It grows between 2 to 6 inches tall and up to 12 inches wide. It has small white blooms that adorn the garden every spring. Irish moss is typically grown in U.S. Department of Agriculture plant hardiness zones 4 to 8. Plant Irish moss in an area that receives little to no foot traffic and is in partial to full sun.
Determine how many Irish moss plants you need to grow to fill in your desired area. Irish mosses are planted between 6 and 12 inches apart. The closer they are planted together, the quicker they will fill the space.
Purchase and plant Irish moss in the spring when temperatures reach above freezing and frost is not an issue. Irish moss usually can be purchased from spring until fall, but it will thrive if planted in the spring and given an entire growing season before winter.
Buy Irish moss plants at a nursery center, usually available in 3- to 6-inch pots. Look for plants that are green and firm (not wilted). You also can buy Irish moss online or through a nursery catalog, if desired.