Make your own green rooftop in 3 simple steps:    1. In fall, scrape a handful of green moss from a rock or path (or ask a friend to share some).     2. Shred the moss into a blender with 1 cup buttermilk; mix to the consistency of a thick milkshake.     3. Paint the mixture onto the roof, a rock, or other surfaces where you want it to grow and spread. Damp, shaded locations are best. Living Roofs, Living Walls, Pergola, Moss Garden, Small Space Gardening, Earthship, Backyard Projects, Green Building, Outdoor Gardens