I made a separate page devoted to internet “research” on this subject. It may be that a blender slurry of buttermilk and moss is an urban legend as Mossin’ Annie says. I tried to use a food processor and never got to to a slurry state. It ended up as clumps of moss with a buttermilk/liquid mix. I spread it on some Durock and left it behind the house in a moist and shaded area. But I have little hope of it working. I will try the method of the third video on Can You Grow Moss.

What is a proper substrate for a vertical wall? Possibly a fiberglass window screen smeared with a clay and dirt mixture – attached to a stronger wood or wire structure.
Or clay and mortar for something more durable.

Many sources on the web claim that one can put moss and buttermilk into a blender and then paint the slurry onto a substrate that will grow moss within a week or so. Mossin’ Annie, who sells mosses and establishes moss gardens say that this is an urban legend that will only result in a sticky mess. But several sources show moss graffiti images. So I am going to try the experiment using 2 mosses that grow freely in my yard. I have purchased several substrates to use. Each must be strong enough to hold up against wind and weather as a vertical wall.

• Cement board
• Recycled rubber mat
• Polyester mat
• Wire mesh with mortar mix

I have also purchased a misting system with a charcoal filter and timer to run off my garden hose. The charcoal filter is to remove chlorine and other city chemicals that might damage the mosses. I did not intend to use galvanized wire mesh as zinc is supposed to prevent moss growth. But since I have some and it is so common, I will coat it in concrete to see if that is enough coating to prevent contact with the moss.

Quotes from various sources

Moss Gardening Annie Martin p24: Mosses play a significant role in global carbon cycle as the largest land repository for carbon on the planet. Spagnum peatlands soak up vast amounts of carbon dioxide from the air, far exceeding the rate of carbon sequestration by all rainforests combined.

Global carbon cycle would be aided the best through Carbon Recycling. It has been estimated that mosses can sequester between 200 to 500 billion tons of carbon per year. Regrowth of mosses can be best option to reverse the destruction of decline in the environment on that count.

We have to take as much as 1 trillion tons of carbon dioxide out of the air. V. Ram Ramanathan, professor of climate sciences at Scripps Institution of Oceanography

The Benefits & Ecology of a Moss Lawn Cathy Burk Moss is also a bioindicator, meaning that the presence or absence of moss can tell us things about the air quality. Moss is sensitive to particulate pollution in the air such as carbon monoxide, sulphur dioxide, CFCs, and nitrogen oxides. Most of these pollutants come from combustion engines in motor vehicles and some manufacturing industries. If you have moss growing in your yard, you likely have cleaner air than sites where moss is not found growing.

Rhizoids are ‘root-like’ structures used for attachment instead of absorption. Nutrient-poor soil, free of loose rocks, leaves, and miscellaneous forest confetti, is a perfect environment for native moss.

I have dispelled the common adage that mosses prefer an acidic soil in the 5.0 to 5.5 range. Moss is often found growing on acidic substrates and this is often noted as an indication of their preference for that pH range. It is more correct to say that other plants don’t prefer pH levels of 5.0 to 5.5, therefore acidic soils promote less competition, thereby allowing moss colonization. Most mosses will colonize a much wider range of pH than other plants, since they do not draw nutrients from substrates, their need for a certain pH range is overstated.

Sites

http://content.yardmap.org/learn/benefits-ecology-moss-lawn/

http://content.yardmap.org/learn/growing-a-moss-lawn/

http://www.mossandstonegardens.com/blog/how-to-grow-moss/

https://www.mosswalls.com/why-moss

https://www.tnnursery.net/moss-collection-grab-bag-for-sale/

https://www.instructables.com/id/How-to-Make-Moss-Graffiti-1/