A reader recently contacted me with an expanding moss problem. She had a tree removed, and instead of grass growing, she was left with an ever-increasing patch of moss. What to do? To answer her question, let's flip it on its head: How can homeowners encourage moss to grow in their lawns?
The question of how to grow moss might seem preposterous to readers whose "keep-up-with-the-Joneses" inspired vision of landscaping is a chemically produced monoculture of non-native grass covering every unpaved or otherwise unplanted inch of their property. But moss actually has a beauty and a function to add to a landscape. (Of course, since the Joneses' only nature activities take place at artificially produced golf courses, they have not seen the glories of moss before).
Moss can actually serve as a grass replacement in damp, shady areas where grass struggles.
In an article posted on gardeningknowhow.com, Bonnie L. Grant writes, "In order to have moss lawns instead of grass, it is necessary to meet a few conditions. Moss requires an acidic environment, compact soil, protected sun to semi-shade and consistent moisture."
As a result, we might infer that a balanced pH soil that is aerated and well-drained with good sun exposure would be unfriendly to moss.
So how would I exchange moss for grass? First, I would take a closer look at why I need to get rid of the moss. Is it possible that the moss is smarter than I am about my site characteristics? In other words, is the moss functioning as an "indicator plant," telling me that it is the best plant for the place? If so, and if I plan to change nothing about the site, perhaps I should reconsider and attempt to nurture, and not destroy the moss.
Second, my experience teaches me that once it is established, moss is resilient. So I would physically remove the moss. (By the way, perhaps I could look for a place to reuse it). Then I would amend the soil characteristics to suit grass. I would mechanically aerate, add volumes of lime and organic fertilizer, and depending on the soil composition, top-dress with either topsoil or organic humus. (There are a number of ways to balance soil pH, and when used as a soil conditioner, much more lime is required than your instincts tell you).
Now, for the moisture, last year's weather did not allow much drying, and we can do little to change that. But look up. Has the tree cover also increased? You cannot move your neighbor's house that sits to the southwest. But by careful pruning of your own trees or, alas, a selective removal, you may be able to change both the shade and moisture characteristics of the site.
So for moss invasions, in some cases it comes down to choosing between lawn and tree.
Joshua Arp is an ISA-certified municipal specialist, Clarks Summit's municipal arborist and an operator of an organic lawn and landscape maintenance business. Reach him at email@example.com.