Peat Moss is a natural product occurring from decomposed sphagnum in peat bogs. It's fluffy, lightweight and can be used in a variety of mixes to help in water retention and as a soil conditioner. Peat Moss has an acidic pH which certain plants such as ferns, blueberries, azaleas and rhododendrons love. Acidic soil can actually change the color of hydrangea blooms.