Philip Edward Lewis wrote in
. edu:


you can encourage moss by creating an acidic environment. One thing
you can do to help innoculate the area is to make a moss milkshake.
Find some moss growing in similar conditions (the full sun) where you
are allowed to collect it (or noone will care... like an uncarred
for parking lot) and mix it with buttermilk in a blender. (find a used
one if you don't want to use the "food" one.) Paint this slurry onto
the areas you want to become mossy, and keep lightly misted until the
moss takes hold.

I've been told buttermilk slurry can get quite stanky.