How can I get moss to grow in the cracks of my shady flagstone patio?Tim Klinger
Tim Klinger, Akron, OH
Moss is perfect for softening the hard lines in a stone patio. Its varied textures and cool greenness can bring distinctive, enduring beauty to any shady refuge.
Photo/Illustration: Allison Starcher
Christine Cook, landscape designer and oner of Mosaics, an ecological design firm, responds: Moss loves to grow in crevices, infusing a place with a primordial quality and changing the character of any patio as it creeps into corners and cracks, forms green pillows, and promotes an overall feeling of tranquility. For a shady flagstone patio I recommend a moss that prefers less light and is low in stature (some mosses can reach up to 6 inches thick), like an easy-going pioneer moss, which grows well in diverse conditions and reproduces prolifically by spores. If you do not already have a pioneer moss to divide and transplant on your own property, you can find them at specialty and mail-order nurseries; just be sure they have been nursery propagated and not collected from the wild. Two excellent species are Plagiomnium cuspidatum (USDA Hardiness Zones 2–9), a quick spreader with lemon-lime-colored sporophytes (the spore-producing, reproductive parts of moss), and Atrichum angustatum (Zones 4–9), a more drought-tolerant moss with stiff burgundy sporophytes in autumn.
To garden successfully with mosses, I recommend having your soil pH tested and amending it to achieve the preferred pH range of most mosses—4.5 to 6.0. The best time to plant moss is in late spring in a 20/80 mixture of sand and soil with a high iron content. The telltale sign that iron is present in your soil is an orange coloration. If your soil doesn’t have this orange hue, ask at your local garden center for a high-iron soil amendment. To plant the moss, press it carefully into the moistened soil and tamp it gently to remove all air pockets. To give a natural look, plant the moss randomly while maintaining visual continuity. A word to the wise: Wet moss can be slippery, so avoid planting it in high-traffic areas.
Since moss has no roots, water the newly planted area about every other day for the first growing season. Avoid overwatering, however, as this can lead to moss rot and encourage algae to grow on the stone. Once established, the moss will need a sprinkle of water about once a week.
Moss is not maintenance free. It is important to keep it weeded so that it is not taken over by rampant thugs. Moss is evergreen and needs to photosynthesize, so keep leaves and other debris off it. To accelerate growth and keep it lush, spray your moss with a mixture of one quart of buttermilk to two gallons of water twice a year, in spring and again in autumn.