Hi Ken, Here in northern CA, our winters are wet and cool and the perfect conditions for growing moss. I have the moss issue every year. My strategy is to ignore the moss unless it gets too thick. When it's too thick, I just pull off the moss, along with the top layer of media that the moss "roots" are attached to. Then I replace with fresh media. This works for about a year. The next year the moss comes back in full force. The only way to keep the plants moss-free is to repot with fresh medium every 2 years. Here are two photo of a very mossy pot. You are right that if the moss is allowed to get too thick, the seedlings will suffer and in many cases get snuffed out and die. Irids and others deal with this fine but Lachenalia suffer the most. http://flickr.com/photos/xerantheum/… http://flickr.com/photos/xerantheum/… Nhu Berkeley, CA On Tue, Jan 31, 2012 at 10:22 PM, Ken <kjblack@pacbell.net> wrote: > I've had problems this year with algae and moss infesting the top layer of > my outdoor seedling pots and trays, which seems to be detrimental to some > of the seedlings. >