Because moss lacks traditional vascular structures of true leaves, stems, and roots, its growth is limited to moist locations, since their cells must absorb water directly from the air or the ground, moist locations suit them well. Moss also absorbs the nutrients it needs from the air, not from the ground as most plants do. An interesting side note to consider is that without water, fertilization cannot occur in mosses.
All you need to know on moss and on how to grow it here
