Groundcovers are lovely when winding through a garden path of stepping stones, and these miniature workhorses also benefit the yard in less obvious ways. Groundcovers smother weeds that sprout, uninvited, between pavers. They soften the hard edges of a step, and connect garden areas that otherwise would be divided by a path. During the rainy seasons, groundcovers allow water to absorb into the soil, rather than erode the dirt between slabs of flagstone or concrete.
Not every groundcover is appropriate around stepping stones. Some grow too high; some will not survive an accidental misstep. Others are rough on bare feet. Choose a variety that will stay low (6 inches high at most). Avoid plants that are sensitive to alkaline conditions; new pavers and some types of stone will often leach lime into the surrounding soil. Consider the amount of sun or shade a plant will receive, as well as dry or moist soil conditions.
Steps, whether they are brick, stone or concrete, will absorb the heat of the sun. In summertime, this heat will quickly dehydrate a newly planted groundcover, so planting after the heat of high summer allows the root system to develop throughout the fall and the following spring. In shadier sites, dehydration may not be as much of a problem. However, any new groundcover planting needs careful monitoring; these plants often have shallow root systems and are very susceptible to drying out.
Fortunately, most groundcovers will also establish quickly when planted in prepared, amended soil. New plants should be spaced 6 to 12 inches apart. Never force a root ball into areas too small for it; dig the planting hole in another place. A well-planted groundcover will eventually spread wherever it is needed
Groundcovers for Shade
A surprising number of groundcovers do well in shadier areas. Sweet woodruff (Galium odorata) is a fast-growing, aromatic plant with whorled leaves and white summertime flowers. It thrives in USDA zones 4 to 8, even becoming a reseeding pest in rich soils. Dead nettle (Lamium maculatum 'Beacon Silver')--a lovely, hardy plant despite the harsh name--has silver leaves edged in green, creating a luminous pathway in darker areas. The soft pink flowers in spring add an ethereal touch to cottage gardens.
Erica Glasener, in Fine Gardening magazine, recommends Mazus reptans for its quick but non-invasive growth. Mazus reptans also puts on a show of blue, snapdragon-shaped flowers in spring, and is hardy from USDA zones 5 to 8.
Groundcovers for Sun
Perhaps one of the most popular and widely used groundcovers for sunny areas is woolly thyme (Thymus pseudolanuginosus). This tough little plant is related to the culinary herb, and releases a pleasant scent when stepped on. It is drought tolerant, hardy in most zones and spreads up to 3 feet wide as a low mat of small, green-gray leaves.
For smaller areas, creeping thyme (Thymus praecox) is a better choice and, as a bonus, will put on a long display of tiny purple or pink flowers. Irish moss (Sagina subulata) is quite soft and moss-like in appearance, but requires good drainage and sun to thrive. It is hardy from USDA zones 4 to 10 and needs regular water.
Many groundcovers aren't satisfied with simply surrounding a stepping stone, and will grow into other areas if not controlled. Edging a pathway with a plastic barrier will rein in plants that spread via underground rhizomes or roots, but such a barrier will not bother a groundcover that roots where its tendrils touch the ground, like Vinca major and Vinca minor. Be aware of a groundcover's growth habits before planting; once a groundcover is established between stones or pavers, it is difficult to eradicate.