I am in southern NH. One method I have used to get moss to grow on my 60 mil rubber liner (and other surfaces) is to grind up some moss until you have enough to fill a one gallon pail. Then add one can of beer (use one that a friend gave you that you don't like...we all have one of those right) and then add 32 ounces of plain yogurt. Mix this up into a paste, you can add a little water, or a little more beer. Smear this on any surface about a half inch thick, then wet your moss and press it into the mixture. Don't water it for a few days unless your temps are over 85 degrees then just light watering.