rswann Thank you so much!

CoorItalia Most organic growth on roof tiles is either lichen or moss. Lichen is a sign of good air quality as air pollution will kill it. It does not attack or deteriorate a terracotta roof tile (as hundred year tiles in Europe prove!) and, unless you do not like the look then you can wash them off. Having said that we have had customers ask us how to "speed up" the growth of lichen as it does add an antique look. The answer is beer and yogurt! Moss is another organic growth. It is a rootless plant that likes damp conditions so you will find it primarily of shady sides of the roof. Again, it will not damage the tiles, but plenty of growth might move or shift the tiles. Up to you if you want to peel it off. It removes easily.