Having spent the morning organising images for upcoming courses, I was reminded of a regular problem with learning anything practical from nature. There is a real tendency to bias. By which I mean when we are learning something new there is a great temptation to either make our observations fit our predictions, or to overlook things until we find something that looks the way we want it to.
Moss on trees and buildings is a great example of this. The popular notion is that moss will grow on the north side. This is sometimes true, but often not and for a good reason. The harsh truth is that moss doesn’t care where north is at all. Moss will grow where moisture is retained and this is determined by rain, sun, wind and other factors. If it was only about the sun then it would be a far better indicator of north.
To avoid putting too much of a dampener, forgive me, on the spirits of those who like to cling to the north moss theory, here is a nice picture taken near my home looking east at a tree trunk. Lots of moss on the north side, next to none on the south.