Beautiful carpeting the soil in terrariums or in-between steppingstones in mild, frost-free climates, Irish moss (Soleirolia soleirolii) makes a great alternative to lawn grass in shady, moist locations. Other names for this perennial plant include baby's tears and mind-your-own-business. Grow it outdoors in U.S. Department of Agriculture winter hardiness zones 9 and warmer.
Irish moss is native to the islands of the western Mediterranean, growing in shaded pockets of cool, moist soils in the forests. It is widely naturalized across Western Europe today.
Growing only 2 inches tall but spreading its stems indefinitely across the ground, Irish moss is an evergreen perennial with tiny round leaves that are no larger than a quarter-inch in diameter. The stems that hold the leaves are translucent pale green, sometimes blushed with tints of pink. In summer, little tubular flowers appear, emerging from the bases of leaves. The blossoms have four lobes and are white with hints of pink. Normally evergreen, light winter frosts will kill foliage back, but it will quickly rejuvenate in spring. It will be fully killed if temps drop below 23 degrees F, according to the "A-Z Encyclopedia of Garden Plants."
Irish moss is not a real moss. True mosses do not flower but produce spores-like ferns. Irish moss is a member of the nettle family, Urticaceae. An alternate, synonymous botanical name for this species is Helxine soleirolii.
Grow Irish moss in a fertile, moist but well-draining soil that is watered freely in the warmth of summer but slightly less during winter. It grows in both full sun exposures as well as in partial shade situations, such as under trees and arbors. In regions with arid air or hot, intense summer sun rays, more soil moisture or more shading is needed to keep the plants looking most attractive.
Once established in a landscape, Irish moss grows vigorously, even in rather infertile soils or unmaintained areas. This causes it to become a weedy, if not a noxious, invasive plant. It is difficult to eradicate.