Moss does not only grow on the north side of trees, as it is commonly believed by many. Moss typically grows on the north side but this rule only applies in the northern hemisphere. In the southern hemisphere, moss mostly grows on the south side of trees. The reason for this inversion is that in the northern hemisphere, because of the tilt of the Earth on its axis, the sun almost always appears to be a little south of directly overhead. That’s why rooms with windows facing south are brighter than rooms with windows facing north. This is important for moss because the north sides of trees within the northern hemisphere are shadier and therefore wetter. The south sides of trees get more sunlight, so water evaporates faster there