Why a moss wall or moss picture indoors? In Japanese Zen, moss is a symbol of peace, calm and permanence. In western philosophy, plants and the colour green represent freshness, strength and renewal. It is the combination of these which gave rise to the vertical greening systems in our GREEN product line: moss walls, moss pictures and plant walls. In the main highly functionally acoustic, there’s one thing they all have in common: they don’t need any maintenance or care and they’re made in Germany.