In 1965, a few years before his retirement as University of Maine’s distinguished field botanist and plant taxonomist, Dr. Charles Richards purchased property on Great Wass Island, Maine, and immediately began planting native trees in pockets of soil between the granite outcrops. Over time, he exposed more of the granite, saving the peat for soil amendment, and filled in the depressions among the rock with loam and compost to create the foundation of a garden. He hauled stones by boat from outlying islands to form garden paths.
Earlier this summer, Marjorie and I had the unique pleasure of visiting Dr. Richards, accompanying him on a stroll through his garden. Now 92 years young, he lead us along the winding paths through an acre or more of garden beds. We were surrounded by the bright pinks, reds, and whites of astilbes, by daylilies, hostas, daisies, rhododendrons, Japanese maples, and other plants, some native, some exotic. Native bees were everywhere, drawn to the abundance of nectar and pollen.
A gardener’s passion for plants surrounded us. “I enjoy just seeing what will grow here,”, he told us. “My goal is to integrate native vegetation with exotic species.”
We came to the edge of this sea of color and suddenly found ourselves in the cool shade of tall spruce, some of the trees planted by Dr. Richards over 40 years ago. The granite buttresses surrounding the trees were covered with a thick layer of sun-dappled moss that invited us to stop and rest a while.
I often receive letters and emails from gardeners frustrated by moss creeping into shady garden spots where they are trying to grow grass. I give it to them straight, there are only two choices, eliminate the shade and make sure the soil pH has not become too acidic for grass, or cultivate the moss.
Personally, I’ll take moss over lawn grass any day.
My experience with moss gardening is limited to watching moss grow in Marjorie’s garden. Carpets of yellow-green sphagnum moss and grey foliose lichens begin at the edge of the woods and encroach into the paths around the garden beds wherever there is too much shade for grass. Other species of moss form dark green pincushions covering rocks and filling the spaces between surface tree roots, taking advantage of any small niche where other plants would fail to root.
Mosses like it cool, shady, and wet, thriving in thin, nutrient-poor, acidic soil, taking over wherever grasses wane. For a while it may seem as if the two groundcovers are waging a battle for the same spot of ground, but not really. Something has changed – more shade, more water – and the site is in transition. The mosses are destined to win.
Can this process be expedited? Can the gardener establish a moss carpet by encouraging mosses already present in a weakening grass lawn? This is the question posed by George Schenk in his book, “Moss Gardening”. His advice: “Pluck out the wan remnants of grass and greet the moss as friend.”
Acidification of the soil will encourage mosses while discouraging the grass. This can by achieved by dusting the area with powdered sulfur, about 2 ½ pounds per 100 square feet, striving for a pH of 5.5. Or dust the ground with skimmed milk powder or aluminum sulfate, or sprinkle the area with rhododendron fertilizer. All of these materials will help acidify the soil. Be sure to lightly hose any of these powders into the soil, particularly if conditions are dry.
Aside from acidifying the soil, keeping the area groomed will help the moss become established. Pluck out weeds, including tree seedlings and grass plants. And keep the site raked free of tree leaves, pine needles, spruce cones, and other smothering debris. Use rakes with wire or bamboo tines, raking lightly to avoid disturbing the moss.
Once the moss carpet is established, I would be inclined to let nature take its course, to invite debris back into the picture. I enjoy coming across patches of moss strewn with newly fallen pine needles or colorful autumn leaves; and finding piles of spruce cone scales left by a hungry chipmunk or red squirrel – one could hardly find a better place to dine than a soft patch of sphagnum at the edge of the garden.
Dr. Richards’ beautiful garden is featured in my upcoming book, The New England Gardener’s Year. You can find more information about the book as well as seasonal gardening tips at http://www.facebook.com/negardener