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Moss pH preference
The short version: moss tolerates a far wider pH range than most plants. Acidic ground helps because your grass and weeds hate it, not because the moss loves it. Which is why the practical advice is to leave the soil poor and compact it, rather than improve it.
I feel very fortunate to be in the position to ask anything of David Spain, moss expert, co-owner of Moss and Stone Gardens. Often, when I’m researching a piece for this blog or another media outlet, I’ve learned to question long held beliefs. David has taught me think about moss and to question what is being spread by word of mouth.. At first, I felt confident in my understanding of what is widely written about. However, I’ve learned to ask anything of David to better understand exactly how moss grows and thrives. After all, he is the moss expert; I am the communicator. A classic example of this is the pH preference for mosses. I believed, and what is widely written about, is that moss thrives in a pH between 5.0 – 5.5. Most believe this too, so I asked David Spain, what is the perferred pH of moss? According to David Spain, 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 draw no nutrients from the substrate, their need for a particular pH is overstated. That does not make pH useless to you, it changes what it is for. Lowering the pH of a lawn area with wettable sulfur is still worth doing, not because the moss needs it but because grass and broadleaf weeds do not tolerate it. You are not feeding the moss, you are removing its competition. It is the same reasoning as leaving the soil poor rather than improving it. You too can ask anything of David Spain. If you have a moss question, please let him know by sending an email. 
To learn more about Moss and Stone Gardens – Where Moss Rocks!, see our live moss for landscaping. Or email David Spain at info@mossandstonegardens.com. Pending review by Olivia Milner, practitioner-scientist with a background in sustainability and education.